[clang] 213709e - [CLANG] Fix Static Code Analyzer Concerns with bad bit right shift operation in getNVPTXLaneID()

[via cfe-commits]

Author: Manna, Soumi
Date: 2023-06-22T13:29:28-07:00
New Revision: 213709e7be031751170f04b05203b3228f87850a

URL: https://github.com/llvm/llvm-project/commit/213709e7be031751170f04b05203b3228f87850a
DIFF: https://github.com/llvm/llvm-project/commit/213709e7be031751170f04b05203b3228f87850a.diff

LOG: [CLANG] Fix Static Code Analyzer Concerns with bad bit right shift operation in getNVPTXLaneID()

In getNVPTXLaneID(CodeGenFunction &), the value of LaneIDBits is 4294967295 since function call llvm::Log2_32(CGF->getTarget()->getGridValue().GV_Warp_Size) might return 4294967295.

  unsigned LaneIDBits =
       llvm::Log2_32(CGF.getTarget().getGridValue().GV_Warp_Size);
  unsigned LaneIDMask = ~0u >> (32u - LaneIDBits);

The shift amount (32U - LaneIDBits) might be 33, So it has undefined behavior for right shifting by more than 31 bits.

This patch adds an assert to guard the LaneIDBits overflow issue with LaneIDMask value.

Reviewed By: tahonermann

Differential Revision: https://reviews.llvm.org/D151606

Added: 
    

Modified: 
    clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp

Removed: 
    


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diff  --git a/clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp b/clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp
index cf151025eac5d..ad99d681f54cd 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp
@@ -525,6 +525,7 @@ static llvm::Value *getNVPTXLaneID(CodeGenFunction &CGF) {
   CGBuilderTy &Bld = CGF.Builder;
   unsigned LaneIDBits =
       llvm::Log2_32(CGF.getTarget().getGridValue().GV_Warp_Size);
+  assert(LaneIDBits < 32 && "Invalid LaneIDBits size in NVPTX device.");
   unsigned LaneIDMask = ~0u >> (32u - LaneIDBits);
   auto &RT = static_cast<CGOpenMPRuntimeGPU &>(CGF.CGM.getOpenMPRuntime());
   return Bld.CreateAnd(RT.getGPUThreadID(CGF), Bld.getInt32(LaneIDMask),