Install mc in the msan CI job

The msan job uploads test results to MinIO with `mc cp`, but unlike the test/release/coverage jobs it never installed the mc binary. When MinIO credentials are configured (i.e. after merge) the upload step would fail. Install mc to match the other jobs.
Avoid reading uninitialized end.p for point writes/reads
2026-07-22 18:48:49 -04:00 · 2026-07-22 18:48:46 -04:00 · 2026-07-22 18:42:10 -04:00
6 changed files with 251 additions and 2044 deletions
@@ -38,43 +38,21 @@ jobs:
      matrix:
        include:
          - name: 64-bit-versions
-            runner: ubuntu-latest-amd64
-            arch: amd64
-            llvm_version: "21"
-            msan_url: ""
            cmake_args: -DCMAKE_CXX_FLAGS=-DUSE_64_BIT=1
          - name: debug
-            runner: ubuntu-latest-amd64
-            arch: amd64
-            llvm_version: "21"
-            msan_url: https://minio.weaselab.dev/public/x86_64/msan-toolchain-21.1.8.tar.zst
-            cmake_args: -DCMAKE_BUILD_TYPE=Debug -DMSAN_TOOLCHAIN_PATH=/opt/msan
+            cmake_args: -DCMAKE_BUILD_TYPE=Debug
          - name: simd-fallback
-            runner: ubuntu-latest-amd64
-            arch: amd64
-            llvm_version: "21"
-            msan_url: ""
            cmake_args: -DUSE_SIMD_FALLBACK=ON
          - name: gcc
-            runner: ubuntu-latest-amd64
-            arch: amd64
-            llvm_version: "21"
-            msan_url: ""
            cmake_args: -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++
-          - name: debug-arm64
-            runner: ubuntu-latest-arm64
-            arch: arm64
-            llvm_version: "22"
-            msan_url: https://minio.weaselab.dev/public/aarch64/msan-toolchain-22.1.8.tar.zst
-            cmake_args: -DCMAKE_BUILD_TYPE=Debug -DMSAN_TOOLCHAIN_PATH=/opt/msan
-    runs-on: ${{ matrix.runner }}
+    runs-on: ubuntu-latest-amd64
    steps:
      - uses: actions/checkout@v4

      - uses: actions/cache@v4
        with:
          path: /var/cache/apt/archives
-          key: apt-${{ matrix.arch }}-${{ hashFiles('.gitea/workflows/ci.yml') }}
+          key: apt-amd64-${{ hashFiles('.gitea/workflows/ci.yml') }}

      - name: Install common dependencies
        run: |
@@ -90,21 +68,14 @@ jobs:
        run: |
          . /etc/os-release
          wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
-          echo "deb http://apt.llvm.org/${VERSION_CODENAME}/ llvm-toolchain-${VERSION_CODENAME}-${{ matrix.llvm_version }} main" | sudo tee /etc/apt/sources.list.d/llvm.list
+          echo "deb http://apt.llvm.org/${VERSION_CODENAME}/ llvm-toolchain-${VERSION_CODENAME}-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
          sudo apt-get update -qq
          sudo apt-get install -y \
-            clang-${{ matrix.llvm_version }} llvm-${{ matrix.llvm_version }} lld-${{ matrix.llvm_version }} mold
+            clang-21 llvm-21 lld-21 mold
          for tool in clang clang++ llvm-ar llvm-nm llvm-ranlib llvm-objcopy llvm-cov llvm-symbolizer lld ld.lld; do
-            sudo update-alternatives --install /usr/bin/${tool} ${tool} /usr/bin/${tool}-${{ matrix.llvm_version }} 100
+            sudo update-alternatives --install /usr/bin/${tool} ${tool} /usr/bin/${tool}-21 100
          done

-      - name: Download MSan toolchain
-        if: matrix.msan_url != ''
-        run: |
-          curl -Ls "${{ matrix.msan_url }}" -o /tmp/msan-toolchain.tar.zst
-          sudo mkdir -p /opt/msan
-          sudo tar --zstd -xf /tmp/msan-toolchain.tar.zst -C /opt/msan
-
      - name: Build
        run: |
          export CCACHE_DIR="$GITHUB_WORKSPACE/.ccache"
@@ -145,10 +116,8 @@ jobs:
        include:
          - runner: ubuntu-latest-amd64
            arch: amd64
-            cmake_args: -DMSAN_TOOLCHAIN_PATH=/opt/msan
          - runner: ubuntu-latest-arm64
            arch: arm64
-            cmake_args: ""
    runs-on: ${{ matrix.runner }}
    steps:
      - uses: actions/checkout@v4
@@ -189,25 +158,23 @@ jobs:
          restore-keys: |
            ccache-release-${{ matrix.arch }}-

-      - name: Download MSan toolchain
-        if: matrix.arch == 'amd64'
-        run: |
-          curl -Ls "https://minio.weaselab.dev/public/x86_64/msan-toolchain-21.1.8.tar.zst" -o /tmp/msan-toolchain.tar.zst
-          sudo mkdir -p /opt/msan
-          sudo tar --zstd -xf /tmp/msan-toolchain.tar.zst -C /opt/msan
-
      - name: Build
        run: |
          export CCACHE_DIR="$GITHUB_WORKSPACE/.ccache"
          rm -rf build
-          cmake -S . -B build -G Ninja -DCMAKE_CXX_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_FLAGS=-DNVALGRIND ${{ matrix.cmake_args }}
+          cmake -S . -B build -G Ninja -DCMAKE_CXX_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_FLAGS=-DNVALGRIND
          ninja -C build
          ccache -s

      - name: Test
        run: |
          cd build
-          ctest --no-compress-output --test-output-size-passed 100000 --test-output-size-failed 100000 -T Test -j "$(nproc)" --timeout 90 > /dev/null
+          # On arm64, valgrind needs the MAKE_MEM_DEFINED client requests for
+          # https://git.weaselab.dev/weaselab/conflict-set/issues/39, but this
+          # build has -DNVALGRIND, which compiles them out. Skip valgrind
+          # tests here; they run annotated in the test job.
+          ctest --no-compress-output --test-output-size-passed 100000 --test-output-size-failed 100000 ${{ matrix.arch == 'arm64' && '-E valgrind' || '' }} -T Test -j "$(nproc)" --timeout 90 > /dev/null
+
      - name: Package
        run: |
          cd build
@@ -251,6 +218,89 @@ jobs:
            --link "https://minio.weaselab.dev/jenkins/conflict-set/${{ gitea.run_number }}/release-${{ matrix.arch }}/Test.xml.zst" \
            | tee -a "$GITHUB_STEP_SUMMARY"

+  msan:
+    runs-on: ubuntu-latest-amd64
+    env:
+      MSAN_VERSION: "21.1.8"
+      MSAN_URL: "https://minio.weaselab.dev/public/x86_64/msan-toolchain-21.1.8.tar.zst"
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/cache@v4
+        with:
+          path: /var/cache/apt/archives
+          key: apt-amd64-${{ hashFiles('.gitea/workflows/ci.yml') }}
+
+      - name: Install dependencies
+        run: |
+          . /etc/os-release
+          wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
+          echo "deb http://apt.llvm.org/${VERSION_CODENAME}/ llvm-toolchain-${VERSION_CODENAME}-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+          sudo apt-get update -qq
+          sudo apt-get install -y \
+            build-essential ccache clang-21 cmake libc6-dbg \
+            llvm-21 lld-21 mold ninja-build python3 zstd
+          sudo curl -Ls "https://minio.weaselab.dev/public/$(uname -m)/mc.RELEASE.2025-08-13T08-35-41Z" \
+            -o /usr/local/bin/mc && sudo chmod +x /usr/local/bin/mc
+          for tool in clang clang++ llvm-ar llvm-nm llvm-ranlib llvm-objcopy llvm-cov llvm-symbolizer lld ld.lld; do
+            sudo update-alternatives --install /usr/bin/${tool} ${tool} /usr/bin/${tool}-21 100
+          done
+
+      - name: Download MSan toolchain
+        run: |
+          curl -Ls "${MSAN_URL}" -o /tmp/msan-toolchain.tar.zst
+          sudo mkdir -p /opt/msan
+          sudo tar --zstd -xf /tmp/msan-toolchain.tar.zst -C /opt/msan
+
+      - uses: actions/cache@v4
+        with:
+          path: .ccache
+          key: ccache-msan-${{ gitea.sha }}
+          restore-keys: |
+            ccache-msan-
+
+      - name: Build
+        run: |
+          export CCACHE_DIR="$GITHUB_WORKSPACE/.ccache"
+          rm -rf build
+          cmake -S . -B build -G Ninja \
+            -DCMAKE_C_COMPILER=clang \
+            -DCMAKE_CXX_COMPILER=clang++ \
+            -DCMAKE_CXX_COMPILER_LAUNCHER=ccache \
+            -DCMAKE_BUILD_TYPE=Debug \
+            -DDISABLE_TSAN=ON \
+            -DUSE_MSAN=ON \
+            -DCMAKE_CXX_FLAGS="-fsanitize=memory -stdlib=libc++ -I/opt/msan/include/c++/v1 -L/opt/msan/lib -UNDEBUG" \
+            -DCMAKE_EXE_LINKER_FLAGS="-stdlib=libc++ -Wl,-rpath,/opt/msan/lib" \
+            -DCMAKE_SHARED_LINKER_FLAGS="-stdlib=libc++ -Wl,-rpath,/opt/msan/lib"
+          ninja -C build
+          ccache -s
+
+      - name: Test
+        run: |
+          cd build
+          ctest --no-compress-output --test-output-size-passed 100000 --test-output-size-failed 100000 -T Test -j "$(nproc)" --timeout 300 > /dev/null
+
+      - name: Upload test results to MinIO
+        if: always()
+        env:
+          MINIO_ACCESS_KEY: ${{ secrets.MINIO_ACCESS_KEY }}
+          MC_HOST_minio: https://${{ secrets.MINIO_ACCESS_KEY }}:${{ secrets.MINIO_SECRET_KEY }}@minio.weaselab.dev
+        run: |
+          if [ -z "$MINIO_ACCESS_KEY" ]; then
+            echo "MinIO credentials not configured; skipping upload"
+            exit 0
+          fi
+          zstd build/Testing/*/Test.xml
+          mc cp build/Testing/*/Test.xml.zst "minio/jenkins/conflict-set/${{ gitea.run_number }}/msan/"
+
+      - name: Test summary
+        if: always()
+        run: |
+          python3 ctest_summary.py build/Testing/*/Test.xml \
+            --link "https://minio.weaselab.dev/jenkins/conflict-set/${{ gitea.run_number }}/msan/Test.xml.zst" \
+            | tee -a "$GITHUB_STEP_SUMMARY"
+
  coverage:
    runs-on: ubuntu-latest-amd64
    steps:
@@ -49,6 +49,18 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
        ${LLVM_OBJCOPY}
        CACHE FILEPATH "path to objcopy binary" FORCE)
  endif()
+  if(USE_MSAN)
+    find_program(LLD_LINKER lld)
+    if(LLD_LINKER)
+      set(CMAKE_LINKER_TYPE
+          "LLD"
+          CACHE STRING "Use LLD linker" FORCE)
+      set(CMAKE_LINKER
+          ${LLD_LINKER}
+          CACHE FILEPATH "path to linker binary" FORCE)
+      add_link_options("-fuse-ld=lld")
+    endif()
+  endif()
 endif()

 if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
@@ -103,12 +115,7 @@ option(USE_SIMD_FALLBACK

 option(DISABLE_TSAN "Disable TSAN" OFF)

-set(MSAN_TOOLCHAIN_PATH
-    ""
-    CACHE
-      PATH
-      "Path to an MSan-instrumented libc++ toolchain. When set, an MSan fuzz_driver target is added. Must contain include/c++/v1 and lib. See build_msan_toolchain.sh to produce one."
-)
+option(USE_MSAN "Build with MemorySanitizer (disables ASan/UBSan)" OFF)

 # This is encouraged according to
 # https://valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.clientreq
@@ -239,8 +246,10 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
  target_compile_definitions(conflict_set_main PRIVATE ENABLE_MAIN)
  target_link_libraries(conflict_set_main PRIVATE nanobench)

-  if(NOT APPLE)
-    # libfuzzer target, to generate/manage corpus
+  if(NOT APPLE AND NOT USE_MSAN)
+    # libfuzzer target, to generate/manage corpus. MSan requires an instrumented
+    # libfuzzer runtime, which is not shipped with the compiler, so skip this
+    # target when building with MSan.
    set(FUZZ_FLAGS "-fsanitize=fuzzer-no-link,address,undefined")
    include(CheckCXXCompilerFlag)
    cmake_push_check_state()
@@ -260,12 +269,17 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
    endif()
  endif()

-  # whitebox tests asan+ubsan
+  # whitebox tests
  add_executable(fuzz_driver ConflictSet.cpp FuzzTestDriver.cpp)
  target_compile_options(fuzz_driver PRIVATE ${TEST_FLAGS})
  if(NOT CMAKE_CROSSCOMPILING)
-    target_compile_options(fuzz_driver PRIVATE -fsanitize=address,undefined)
-    target_link_options(fuzz_driver PRIVATE -fsanitize=address,undefined)
+    if(USE_MSAN)
+      target_compile_options(fuzz_driver PRIVATE -fsanitize=memory)
+      target_link_options(fuzz_driver PRIVATE -fsanitize=memory)
+    else()
+      target_compile_options(fuzz_driver PRIVATE -fsanitize=address,undefined)
+      target_link_options(fuzz_driver PRIVATE -fsanitize=address,undefined)
+    endif()
  endif()
  target_compile_definitions(fuzz_driver PRIVATE ENABLE_FUZZ)
  target_include_directories(fuzz_driver
@@ -275,36 +289,10 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
    add_test(NAME conflict_set_fuzz_${hash} COMMAND fuzz_driver ${TEST})
  endforeach()

-  # whitebox tests msan
-  if(MSAN_TOOLCHAIN_PATH)
-    add_executable(fuzz_driver_msan ConflictSet.cpp FuzzTestDriver.cpp)
-    target_compile_options(fuzz_driver_msan PRIVATE ${TEST_FLAGS})
-    if(NOT CMAKE_CROSSCOMPILING)
-      target_compile_options(
-        fuzz_driver_msan
-        PRIVATE -fsanitize=memory -fsanitize-memory-track-origins=2
-                $<$<COMPILE_LANGUAGE:CXX>:-stdlib=libc++>
-                -I${MSAN_TOOLCHAIN_PATH}/include/c++/v1)
-      target_link_options(
-        fuzz_driver_msan
-        PRIVATE
-        -fsanitize=memory
-        -fsanitize-memory-track-origins=2
-        -stdlib=libc++
-        -L${MSAN_TOOLCHAIN_PATH}/lib
-        LINKER:-rpath,${MSAN_TOOLCHAIN_PATH}/lib)
-    endif()
-    target_compile_definitions(fuzz_driver_msan PRIVATE ENABLE_FUZZ)
-    target_include_directories(fuzz_driver_msan
-                               PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include)
-    foreach(TEST ${CORPUS_TESTS})
-      get_filename_component(hash ${TEST} NAME)
-      add_test(NAME conflict_set_msan_${hash} COMMAND fuzz_driver_msan ${TEST})
-    endforeach()
-  endif()
-
  # tsan tests
-  if(NOT CMAKE_CROSSCOMPILING AND NOT DISABLE_TSAN)
+  if(NOT CMAKE_CROSSCOMPILING
+     AND NOT DISABLE_TSAN
+     AND NOT USE_MSAN)
    add_executable(tsan_driver ConflictSet.cpp FuzzTestDriver.cpp)
    target_compile_options(tsan_driver PRIVATE ${TEST_FLAGS} -fsanitize=thread)
    target_link_options(tsan_driver PRIVATE -fsanitize=thread)
@@ -526,6 +514,11 @@ target_include_directories(
  PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/${PROJECT_NAME}>)

+if(USE_MSAN)
+  target_compile_options(${PROJECT_NAME} PUBLIC -fsanitize=memory)
+  target_link_options(${PROJECT_NAME} PUBLIC -fsanitize=memory)
+endif()
+
 set_target_properties(
  ${PROJECT_NAME} PROPERTIES VERSION ${PROJECT_VERSION}
                             SOVERSION ${PROJECT_VERSION_MAJOR})
@@ -488,7 +488,6 @@ inline void Node3::copyChildrenAndKeyFrom(const Node16 &other) {

 inline void Node16::copyChildrenAndKeyFrom(const Node3 &other) {
  copyCommon(*this, other);
-  memset(index, 0, sizeof(index));
  memcpy(index, other.index, Node3::kMaxNodes);
  memcpy(children, other.children,
         Node3::kMaxNodes * sizeof(children[0])); // NOLINT
@@ -500,12 +499,6 @@ inline void Node16::copyChildrenAndKeyFrom(const Node3 &other) {
    assert(children[i]->parent == &other);
    children[i]->parent = this;
  }
-  // The index bytes beyond numChildren are initialized so that the SIMD loads
-  // of the full 16 bytes are well-defined (reading indeterminate bytes is UB
-  // in C++). valgrind then treats them as undefined so that it can still flag
-  // any read that relies on them.
-  VALGRIND_MAKE_MEM_UNDEFINED(index + numChildren,
-                              sizeof(index) - numChildren * sizeof(index[0]));
 }

 inline void Node16::copyChildrenAndKeyFrom(const Node16 &other) {
@@ -522,7 +515,6 @@ inline void Node16::copyChildrenAndKeyFrom(const Node16 &other) {

 inline void Node16::copyChildrenAndKeyFrom(const Node48 &other) {
  copyCommon(*this, other);
-  memset(index, 0, sizeof(index));
  int i = 0;
  other.bitSet.forEachSet([&](int c) {
    // Suppress a false positive -Waggressive-loop-optimizations warning
@@ -536,12 +528,6 @@ inline void Node16::copyChildrenAndKeyFrom(const Node48 &other) {
    ++i;
  });
  memcpy(partialKey(), &other + 1, partialKeyLen);
-  // The index bytes beyond numChildren are initialized so that the SIMD loads
-  // of the full 16 bytes are well-defined (reading indeterminate bytes is UB
-  // in C++). valgrind then treats them as undefined so that it can still flag
-  // any read that relies on them.
-  VALGRIND_MAKE_MEM_UNDEFINED(index + numChildren,
-                              sizeof(index) - numChildren * sizeof(index[0]));
 }

 inline void Node48::copyChildrenAndKeyFrom(const Node16 &other) {
@@ -549,7 +535,6 @@ inline void Node48::copyChildrenAndKeyFrom(const Node16 &other) {
  assert(numChildren == Node16::kMaxNodes);
  memset(index, -1, sizeof(index));
  memset(children, 0, sizeof(children));
-  memset(reverseIndex, 0, sizeof(reverseIndex));
  const auto z = InternalVersionT::zero;
  for (auto &v : childMaxVersion) {
    v = z;
@@ -569,13 +554,6 @@ inline void Node48::copyChildrenAndKeyFrom(const Node16 &other) {
        std::max(maxOfMax[i >> Node48::kMaxOfMaxShift], childMaxVersion[i]);
    ++i;
  }
-  // The reverseIndex bytes beyond numChildren are initialized so that the
-  // SIMD loads of a full 16-byte page in scan16 are well-defined (reading
-  // indeterminate bytes is UB in C++). valgrind then treats them as undefined
-  // so that it can still flag any read that relies on them.
-  VALGRIND_MAKE_MEM_UNDEFINED(reverseIndex + numChildren,
-                              sizeof(reverseIndex) -
-                                  numChildren * sizeof(reverseIndex[0]));
 }

 inline void Node48::copyChildrenAndKeyFrom(const Node48 &other) {
@@ -602,7 +580,6 @@ inline void Node48::copyChildrenAndKeyFrom(const Node256 &other) {
  copyCommon(*this, other);
  memset(index, -1, sizeof(index));
  memset(children, 0, sizeof(children));
-  memset(reverseIndex, 0, sizeof(reverseIndex));
  const auto z = InternalVersionT::zero;
  for (auto &v : childMaxVersion) {
    v = z;
@@ -624,13 +601,6 @@ inline void Node48::copyChildrenAndKeyFrom(const Node256 &other) {
    ++i;
  });
  memcpy(partialKey(), &other + 1, partialKeyLen);
-  // The reverseIndex bytes beyond numChildren are initialized so that the
-  // SIMD loads of a full 16-byte page in scan16 are well-defined (reading
-  // indeterminate bytes is UB in C++). valgrind then treats them as undefined
-  // so that it can still flag any read that relies on them.
-  VALGRIND_MAKE_MEM_UNDEFINED(reverseIndex + numChildren,
-                              sizeof(reverseIndex) -
-                                  numChildren * sizeof(reverseIndex[0]));
 }

 inline void Node256::copyChildrenAndKeyFrom(const Node48 &other) {
@@ -1362,8 +1332,8 @@ TaggedNodePointer getChildGeq(Node *self, int child) {

 TaggedNodePointer getFirstChild(Node0 *) { return nullptr; }
 TaggedNodePointer getFirstChild(Node3 *self) {
-  // Don't prefetch since self->children[1] might be uninitialized and msan
-  // doesn't like that
+  // Improves scan performance
+  self->children[1].prefetch();
  return self->children[0];
 }
 TaggedNodePointer getFirstChild(Node16 *self) {
@@ -2025,8 +1995,6 @@ Node *erase(Node *self, WriteContext *writeContext, bool logical) {
    parent48->childMaxVersion[lastChildrenIndex] = writeContext->zero;
    VALGRIND_MAKE_MEM_UNDEFINED(parent48->children + lastChildrenIndex,
                                sizeof(parent48->children[0]));
-    VALGRIND_MAKE_MEM_UNDEFINED(parent48->reverseIndex + lastChildrenIndex,
-                                sizeof(parent48->reverseIndex[0]));

    if (needsDownsize(parent48)) {
      downsize(parent48, writeContext);
@@ -2119,52 +2087,6 @@ compare16_avx512(const InternalVersionT *vs, InternalVersionT rv) {
 }
 #endif

-#ifdef HAS_ARM_NEON
-// Returns a uint8x16_t whose byte i is 0xff if vs[i] > readVersion and 0
-// otherwise. When USE_64_BIT is set the comparison uses the full 64-bit value
-// (via vcgtq_s64); otherwise it falls back to the 32-bit subtract-and-compare
-// used by the original NEON fast path. The caller narrows this 16-byte vector
-// into the nibble-packed (4 bits per version) mask expected by scan16 and
-// checkMaxBetweenExclusiveImpl.
-inline uint8x16_t conflictMask16(const InternalVersionT *vs,
-                                 InternalVersionT readVersion) {
-#if USE_64_BIT
-  int64_t rv;
-  memcpy(&rv, &readVersion, sizeof(rv));
-  const auto rvVec = vdupq_n_s64(rv);
-  int32x2_t r32[8];
-  const auto *vsp = reinterpret_cast<const int64_t *>(vs);
-  for (int j = 0; j < 8; ++j) {
-    r32[j] = vmovn_s64(vcgtq_s64(vld1q_s64(vsp + 2 * j), rvVec));
-  }
-  uint32x4_t w4[4];
-  for (int k = 0; k < 4; ++k) {
-    w4[k] = vreinterpretq_u32_s32(vcombine_s32(r32[2 * k], r32[2 * k + 1]));
-  }
-  return vcombine_u8(
-      vmovn_u16(vcombine_u16(vmovn_u32(w4[0]), vmovn_u32(w4[1]))),
-      vmovn_u16(vcombine_u16(vmovn_u32(w4[2]), vmovn_u32(w4[3]))));
-#else
-  uint32x4_t w4[4];
-  memcpy(w4, vs, sizeof(w4));
-  uint32_t rv;
-  memcpy(&rv, &readVersion, sizeof(rv));
-  const auto rvVec = vdupq_n_u32(rv);
-
-  int32x4_t z;
-  memset(&z, 0, sizeof(z));
-
-  uint16x4_t conflicting[4];
-  for (int i = 0; i < 4; ++i) {
-    conflicting[i] =
-        vmovn_u32(vcgtq_s32(vreinterpretq_s32_u32(vsubq_u32(w4[i], rvVec)), z));
-  }
-  return vcombine_u8(vmovn_u16(vcombine_u16(conflicting[0], conflicting[1])),
-                     vmovn_u16(vcombine_u16(conflicting[2], conflicting[3])));
-#endif
-}
-#endif
-
 // Returns true if v[i] <= readVersion for all i such that begin <= is[i] < end
 // Preconditions: begin <= end, end - begin < 256
 template <bool kAVX512>
@@ -2185,10 +2107,26 @@ bool scan16(const InternalVersionT *vs, const uint8_t *is, int begin, int end,
  uint64_t mask = vget_lane_u64(
      vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(results), 4)), 0);

+  uint32x4_t w4[4];
+  memcpy(w4, vs, sizeof(w4));
+  uint32_t rv;
+  memcpy(&rv, &readVersion, sizeof(rv));
+  const auto rvVec = vdupq_n_u32(rv);
+
+  int32x4_t z;
+  memset(&z, 0, sizeof(z));
+
+  uint16x4_t conflicting[4];
+  for (int i = 0; i < 4; ++i) {
+    conflicting[i] =
+        vmovn_u32(vcgtq_s32(vreinterpretq_s32_u32(vsubq_u32(w4[i], rvVec)), z));
+  }
+  auto combined =
+      vcombine_u8(vmovn_u16(vcombine_u16(conflicting[0], conflicting[1])),
+                  vmovn_u16(vcombine_u16(conflicting[2], conflicting[3])));
+
  uint64_t compared = vget_lane_u64(
-      vreinterpret_u64_u8(vshrn_n_u16(
-          vreinterpretq_u16_u8(conflictMask16(vs, readVersion)), 4)),
-      0);
+      vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(combined), 4)), 0);

  return !(compared & mask);

@@ -2215,14 +2153,12 @@ bool scan16(const InternalVersionT *vs, const uint8_t *is, int begin, int end,
  auto inBounds = [&](unsigned c) { return c - shiftAmount < shiftUpperBound; };

  uint32_t compared = 0;
+  for (int i = 0; i < 16; ++i) {
+    compared |= (vs[i] > readVersion) << i;
+  }
  uint32_t mask = 0;
  for (int i = 0; i < 16; ++i) {
-    if (vs[i] > readVersion) {
-      compared |= 1u << i;
-      if (inBounds(is[i])) {
-        mask |= 1u << i;
-      }
-    }
+    mask |= inBounds(is[i]) << i;
  }
  return !(compared & mask);

@@ -2238,10 +2174,26 @@ bool scan16(const InternalVersionT *vs, int begin, int end,
  assert(begin <= end);

 #if defined(HAS_ARM_NEON)
+  uint32x4_t w4[4];
+  memcpy(w4, vs, sizeof(w4));
+  uint32_t rv;
+  memcpy(&rv, &readVersion, sizeof(rv));
+  const auto rvVec = vdupq_n_u32(rv);
+
+  int32x4_t z;
+  memset(&z, 0, sizeof(z));
+
+  uint16x4_t conflicting[4];
+  for (int i = 0; i < 4; ++i) {
+    conflicting[i] =
+        vmovn_u32(vcgtq_s32(vreinterpretq_s32_u32(vsubq_u32(w4[i], rvVec)), z));
+  }
+  auto combined =
+      vcombine_u8(vmovn_u16(vcombine_u16(conflicting[0], conflicting[1])),
+                  vmovn_u16(vcombine_u16(conflicting[2], conflicting[3])));
+
  uint64_t conflict = vget_lane_u64(
-      vreinterpret_u64_u8(vshrn_n_u16(
-          vreinterpretq_u16_u8(conflictMask16(vs, readVersion)), 4)),
-      0);
+      vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(combined), 4)), 0);

  conflict &= end == 16 ? -1 : (uint64_t(1) << (end << 2)) - 1;
  conflict >>= begin << 2;
@@ -2298,9 +2250,17 @@ bool checkMaxBetweenExclusiveImpl(Node3 *n, int begin, int end,
  auto inBounds = [&](unsigned c) { return c - shiftAmount < shiftUpperBound; };

  uint32_t mask = 0;
-  for (int i = 0; i < self->numChildren; ++i) {
+  for (int i = 0; i < Node3::kMaxNodes; ++i) {
    mask |= inBounds(self->index[i]) << i;
  }
+  mask &= (1 << self->numChildren) - 1;
+#ifdef __aarch64__
+  // The bits surviving the mask above don't derive from uninitialized slots,
+  // but clang 21+ on aarch64 lowers inBounds through flags+csel, which
+  // memcheck models imprecisely, tainting bits the mask provably clears.
+  // https://git.weaselab.dev/weaselab/conflict-set/issues/39
+  VALGRIND_MAKE_MEM_DEFINED(&mask, sizeof(mask));
+#endif
  if (!mask) {
    return true;
  }
@@ -2308,11 +2268,17 @@ bool checkMaxBetweenExclusiveImpl(Node3 *n, int begin, int end,
  const bool firstRangeOk =
      !child->entryPresent || child->entry.rangeVersion <= readVersion;
  uint32_t compared = 0;
-  for (int i = 0; i < self->numChildren; ++i) {
+  for (int i = 0; i < Node3::kMaxNodes; ++i) {
    compared |= (self->childMaxVersion[i] > readVersion) << i;
  }

-  return !(compared & mask) && firstRangeOk;
+  uint32_t compared_masked = compared & mask;
+#ifdef __aarch64__
+  // Same imprecise csel modeling as above.
+  // https://git.weaselab.dev/weaselab/conflict-set/issues/39
+  VALGRIND_MAKE_MEM_DEFINED(&compared_masked, sizeof(compared_masked));
+#endif
+  return !compared_masked && firstRangeOk;
 }

 template <bool kAVX512>
@@ -2355,11 +2321,26 @@ bool checkMaxBetweenExclusiveImpl(Node16 *n, int begin, int end,
  const bool firstRangeOk =
      !child->entryPresent || child->entry.rangeVersion <= readVersion;

+  uint32x4_t w4[4];
+  memcpy(w4, self->childMaxVersion, sizeof(w4));
+  uint32_t rv;
+  memcpy(&rv, &readVersion, sizeof(rv));
+  const auto rvVec = vdupq_n_u32(rv);
+
+  int32x4_t z;
+  memset(&z, 0, sizeof(z));
+
+  uint16x4_t conflicting[4];
+  for (int i = 0; i < 4; ++i) {
+    conflicting[i] =
+        vmovn_u32(vcgtq_s32(vreinterpretq_s32_u32(vsubq_u32(w4[i], rvVec)), z));
+  }
+  auto combined =
+      vcombine_u8(vmovn_u16(vcombine_u16(conflicting[0], conflicting[1])),
+                  vmovn_u16(vcombine_u16(conflicting[2], conflicting[3])));
+
  uint64_t compared = vget_lane_u64(
-      vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(conflictMask16(
-                                          self->childMaxVersion, readVersion)),
-                                      4)),
-      0);
+      vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(combined), 4)), 0);

  return !(compared & mask) && firstRangeOk;

@@ -2394,9 +2375,10 @@ bool checkMaxBetweenExclusiveImpl(Node16 *n, int begin, int end,
  auto inBounds = [&](unsigned c) { return c - shiftAmount < shiftUpperBound; };

  uint32_t mask = 0;
-  for (int i = 0; i < self->numChildren; ++i) {
+  for (int i = 0; i < 16; ++i) {
    mask |= inBounds(self->index[i]) << i;
  }
+  mask &= (1 << self->numChildren) - 1;
  if (!mask) {
    return true;
  }
@@ -2404,7 +2386,7 @@ bool checkMaxBetweenExclusiveImpl(Node16 *n, int begin, int end,
  const bool firstRangeOk =
      !child->entryPresent || child->entry.rangeVersion <= readVersion;
  uint32_t compared = 0;
-  for (int i = 0; i < self->numChildren; ++i) {
+  for (int i = 0; i < 16; ++i) {
    compared |= (self->childMaxVersion[i] > readVersion) << i;
  }
  return !(compared & mask) && firstRangeOk;
@@ -3892,9 +3874,8 @@ void Job::init(const ConflictSet::ReadRange *read, ConflictSet::Result *result,
    this->result = result;
    continuation = check::point_read_state_machine::begin;
  } else {
-    auto end = TrivialSpan(read->end.p, read->end.len);
    this->begin = begin;
-    this->end = end;
+    this->end = TrivialSpan(read->end.p, read->end.len);
    this->n = root;
    this->readVersion = InternalVersionT(read->readVersion);
    this->result = result;
@@ -7,10 +7,10 @@ Hardware for all benchmarks is an AMD Ryzen 9 7900 with (2x32GB) 5600MT/s CL28-3
 ```
 $ clang++ --version

-Ubuntu clang version 21.1.8 (6ubuntu1)
+Ubuntu clang version 20.0.0 (++20241120082228+86734c857724-1~exp1~20241120202359.554)
 Target: x86_64-pc-linux-gnu
 Thread model: posix
-InstalledDir: /usr/lib/llvm-21/bin
+InstalledDir: /usr/lib/llvm-20/bin
 ```

 # Microbenchmark
@@ -19,30 +19,30 @@ InstalledDir: /usr/lib/llvm-21/bin

 |               ns/op |                op/s |    err% |          ins/op |          cyc/op |    IPC |         bra/op |   miss% |     total | benchmark
 |--------------------:|--------------------:|--------:|----------------:|----------------:|-------:|---------------:|--------:|----------:|:----------
-|              164.29 |        6,086,873.38 |    0.0% |        3,107.03 |          604.19 |  5.142 |         558.59 |    0.0% |      1.96 | `point reads`
-|              161.05 |        6,209,395.38 |    0.1% |        3,036.76 |          592.21 |  5.128 |         539.35 |    0.0% |      1.93 | `prefix reads`
-|              239.55 |        4,174,539.38 |    0.1% |        3,722.71 |          880.68 |  4.227 |         692.00 |    0.0% |      2.86 | `range reads`
-|              354.75 |        2,818,919.14 |    0.7% |        4,523.64 |        1,304.75 |  3.467 |         720.22 |    2.0% |      4.23 | `point writes`
-|              345.32 |        2,895,878.47 |    0.1% |        4,484.57 |        1,270.31 |  3.530 |         705.00 |    1.8% |      4.12 | `prefix writes`
-|              193.48 |        5,168,547.42 |    0.1% |        2,224.10 |          711.72 |  3.125 |         377.17 |    3.3% |      2.32 | `range writes`
-|              404.89 |        2,469,777.50 |    2.4% |        6,855.96 |        1,489.70 |  4.602 |       1,227.82 |    1.3% |      0.05 | `monotonic increasing point writes`
-|          134,231.80 |            7,449.80 |    1.9% |      812,045.25 |      495,770.40 |  1.638 |     151,246.50 |    0.9% |      0.01 | `worst case for radix tree`
-|               37.80 |       26,454,311.17 |    0.4% |          701.00 |          139.14 |  5.038 |         102.00 |    0.0% |      0.01 | `create and destroy`
+|              161.29 |        6,200,056.17 |    0.1% |        3,014.03 |          831.04 |  3.627 |         504.59 |    0.0% |      1.93 | `point reads`
+|              158.32 |        6,316,160.64 |    0.1% |        2,954.16 |          815.80 |  3.621 |         490.17 |    0.0% |      1.89 | `prefix reads`
+|              237.39 |        4,212,409.50 |    0.2% |        3,592.41 |        1,233.96 |  2.911 |         629.31 |    0.0% |      2.84 | `range reads`
+|              442.11 |        2,261,878.94 |    0.0% |        4,450.57 |        2,314.25 |  1.923 |         707.92 |    2.1% |      5.28 | `point writes`
+|              439.89 |        2,273,308.53 |    0.1% |        4,410.22 |        2,302.29 |  1.916 |         694.74 |    2.1% |      5.25 | `prefix writes`
+|              290.96 |        3,436,936.78 |    0.0% |        2,315.38 |        1,528.68 |  1.515 |         396.69 |    3.3% |      3.49 | `range writes`
+|              476.93 |        2,096,762.02 |    0.6% |        6,999.33 |        2,484.94 |  2.817 |       1,251.73 |    1.3% |      0.06 | `monotonic increasing point writes`
+|          131,736.57 |            7,590.91 |    1.1% |      807,444.50 |      704,941.71 |  1.145 |     144,584.60 |    0.9% |      0.01 | `worst case for radix tree`
+|               45.50 |       21,978,369.95 |    1.1% |          902.00 |          232.36 |  3.882 |         132.00 |    0.0% |      0.01 | `create and destroy`

 ## Radix tree (this implementation)


 |               ns/op |                op/s |    err% |          ins/op |          cyc/op |    IPC |         bra/op |   miss% |     total | benchmark
 |--------------------:|--------------------:|--------:|----------------:|----------------:|-------:|---------------:|--------:|----------:|:----------
-|               12.89 |       77,565,115.56 |    0.1% |          244.55 |           47.43 |  5.155 |          34.21 |    0.6% |      0.15 | `point reads`
-|               15.11 |       66,162,047.76 |    0.1% |          297.79 |           55.60 |  5.356 |          43.23 |    0.4% |      0.18 | `prefix reads`
-|               36.29 |       27,559,358.29 |    0.1% |          783.16 |          133.44 |  5.869 |         109.52 |    0.2% |      0.43 | `range reads`
-|               20.53 |       48,719,405.55 |    0.1% |          381.81 |           75.51 |  5.057 |          51.04 |    0.5% |      0.25 | `point writes`
-|               39.37 |       25,402,042.40 |    0.1% |          685.00 |          144.83 |  4.730 |         106.72 |    0.3% |      0.47 | `prefix writes`
-|               43.78 |       22,843,841.63 |    0.1% |          800.40 |          161.06 |  4.970 |         127.36 |    0.1% |      0.53 | `range writes`
-|               78.37 |       12,760,008.75 |    1.0% |        1,452.61 |          288.24 |  5.040 |         278.69 |    0.1% |      0.01 | `monotonic increasing point writes`
-|          322,885.50 |            3,097.07 |    1.5% |    4,362,382.00 |    1,183,852.00 |  3.685 |     765,301.00 |    0.1% |      0.01 | `worst case for radix tree`
-|               99.99 |       10,000,718.79 |    0.4% |        1,775.00 |          367.93 |  4.824 |         288.00 |    0.0% |      0.01 | `create and destroy`
+|               12.36 |       80,885,626.43 |    0.2% |          243.56 |           63.62 |  3.828 |          31.07 |    0.6% |      0.15 | `point reads`
+|               14.18 |       70,502,196.81 |    0.1% |          297.72 |           73.13 |  4.071 |          40.31 |    0.5% |      0.17 | `prefix reads`
+|               33.44 |       29,901,623.04 |    0.1% |          767.90 |          172.42 |  4.454 |         101.32 |    0.2% |      0.40 | `range reads`
+|               19.48 |       51,342,564.70 |    0.3% |          374.45 |          100.43 |  3.728 |          48.92 |    0.5% |      0.23 | `point writes`
+|               37.46 |       26,694,471.44 |    0.1% |          672.00 |          193.14 |  3.479 |         101.28 |    0.3% |      0.45 | `prefix writes`
+|               38.78 |       25,784,784.34 |    0.0% |          738.26 |          199.93 |  3.693 |         111.59 |    0.1% |      0.47 | `range writes`
+|               76.05 |       13,148,995.74 |    0.7% |        1,450.77 |          397.16 |  3.653 |         275.72 |    0.0% |      0.01 | `monotonic increasing point writes`
+|          286,920.33 |            3,485.29 |    0.4% |    4,117,948.00 |    1,521,352.00 |  2.707 |     714,833.00 |    0.1% |      0.01 | `worst case for radix tree`
+|               95.66 |       10,453,798.72 |    0.5% |        1,986.00 |          495.04 |  4.012 |         315.00 |    0.0% |      0.01 | `create and destroy`

 # "Real data" test

@@ -51,13 +51,13 @@ Point queries only. Gc ratio is the ratio of time spent doing garbage collection
 ## skip list

 ```
-Check: 4.62967 seconds, 352.195 MB/s, Add: 3.34177 seconds, 167.771 MB/s, Gc ratio: 37.9399%, Peak idle memory: 5.51852e+06
+Check: 4.53508 seconds, 371.81 MB/s, Add: 3.81222 seconds, 150.919 MB/s, Gc ratio: 33.66%, Peak idle memory: 5.61007e+06
 ```

 ## radix tree

 ```
-Check: 1.00477 seconds, 1622.8 MB/s, Add: 1.21142 seconds, 462.808 MB/s, Gc ratio: 39.4716%, Peak idle memory: 2.0226e+06
+Check: 0.957735 seconds, 1760.6 MB/s, Add: 1.19942 seconds, 479.678 MB/s, Gc ratio: 38.6069%, Peak idle memory: 2.05667e+06
 ```

 ## hash table
@@ -65,6 +65,6 @@ Check: 1.00477 seconds, 1622.8 MB/s, Add: 1.21142 seconds, 462.808 MB/s, Gc rati
 (The hash table implementation doesn't work on range queries, and its purpose is to provide an idea of how fast point queries can be)

 ```
-Check: 0.854254 seconds, 1908.74 MB/s, Add: 0.632626 seconds, 886.232 MB/s, Gc ratio: 41.0827%, Peak idle memory: 0
+Check: 0.804598 seconds, 2095.69 MB/s, Add: 0.671221 seconds, 857.147 MB/s, Gc ratio: 35.0034%, Peak idle memory: 0
 ```

@@ -13,26 +13,26 @@ cd libcxx-msan

 git clone --depth=1 "https://github.com/llvm/llvm-project.git" -b "release/${LLVM_VERSION}.x"

-cmake -S llvm-project/runtimes -B build_msan \
+cmake -S llvm-project/runtimes -B build \
  -DCMAKE_BUILD_TYPE=Release \
-  -DCMAKE_CXX_COMPILER="clang++-${LLVM_VERSION}" \
  -DCMAKE_C_COMPILER="clang-${LLVM_VERSION}" \
-  -DCMAKE_INSTALL_PREFIX="${MSAN_PREFIX}" \
+  -DCMAKE_CXX_COMPILER="clang++-${LLVM_VERSION}" \
+  -DLLVM_USE_SANITIZER=MemoryWithOrigins \
  -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" \
-  -DLLVM_USE_SANITIZER=MemoryWithOrigins
-
-cmake --build build_msan -j"${JOBS}"
-cmake --install build_msan
-
-cmake -S llvm-project/runtimes -B build_nomsan \
-  -DCMAKE_BUILD_TYPE=Release \
-  -DCMAKE_CXX_COMPILER="clang++-${LLVM_VERSION}" \
-  -DCMAKE_C_COMPILER="clang-${LLVM_VERSION}" \
+  -DLLVM_TARGETS_TO_BUILD=Native \
  -DCMAKE_INSTALL_PREFIX="${MSAN_PREFIX}" \
-  -DLLVM_ENABLE_RUNTIMES="libunwind"
+  -DLIBCXXABI_USE_LLVM_UNWINDER=ON \
+  -DLIBCXXABI_ENABLE_STATIC_UNWINDER=ON \
+  -DLIBCXX_USE_COMPILER_RT=ON \
+  -DLIBCXXABI_USE_COMPILER_RT=ON \
+  -DLIBUNWIND_USE_COMPILER_RT=ON \
+  -DLIBCXX_INCLUDE_TESTS=OFF \
+  -DLIBCXXABI_INCLUDE_TESTS=OFF \
+  -DLIBUNWIND_INCLUDE_TESTS=OFF \
+  -DLIBCXX_ENABLE_CLANG_TIDY=OFF

-cmake --build build_nomsan -j"${JOBS}"
-cmake --install build_nomsan
+cmake --build build -j"${JOBS}"
+cmake --install build

 VERSION="$(clang-"${LLVM_VERSION}" --version | head -n1 | sed -E 's/.*clang version ([0-9.]+).*/\1/')"
 TARBALL="msan-toolchain-${VERSION}.tar.zst"