[all-commits] [llvm/llvm-project] 332f06: [SeparateConstOffsetFromGEP] Don't set unsound inb...

[Fabian Ritter via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 332f0603635d06986d6d3c8c9ba4fee04c7cab18
      https://github.com/llvm/llvm-project/commit/332f0603635d06986d6d3c8c9ba4fee04c7cab18
  Author: Fabian Ritter <fabian.ritter at amd.com>
  Date:   2025-03-18 (Tue, 18 Mar 2025)

  Changed paths:
    M llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
    M llvm/test/CodeGen/AMDGPU/GlobalISel/flat-scratch.ll
    M llvm/test/CodeGen/AMDGPU/constant-address-space-32bit.ll
    M llvm/test/CodeGen/AMDGPU/flat-scratch.ll
    A llvm/test/CodeGen/AMDGPU/fold-gep-offset.ll
    M llvm/test/CodeGen/AMDGPU/memory_clause.ll
    A llvm/test/Transforms/SeparateConstOffsetFromGEP/AMDGPU/preserve-inbounds.ll
    M llvm/test/Transforms/SeparateConstOffsetFromGEP/AMDGPU/split-gep-and-gvn-addrspace-addressing-modes.ll
    M llvm/test/Transforms/SeparateConstOffsetFromGEP/AMDGPU/split-gep-and-gvn.ll
    M llvm/test/Transforms/SeparateConstOffsetFromGEP/AMDGPU/split-gep.ll
    M llvm/test/Transforms/SeparateConstOffsetFromGEP/NVPTX/split-gep-and-gvn.ll
    M llvm/test/Transforms/SeparateConstOffsetFromGEP/NVPTX/split-gep.ll
    M llvm/test/Transforms/SeparateConstOffsetFromGEP/RISCV/split-gep.ll
    M llvm/test/Transforms/StraightLineStrengthReduce/AMDGPU/reassociate-geps-and-slsr-addrspace.ll
    M llvm/test/Transforms/StraightLineStrengthReduce/NVPTX/reassociate-geps-and-slsr.ll

  Log Message:
  -----------
  [SeparateConstOffsetFromGEP] Don't set unsound inbounds flag (#130616)

The language reference says about inbounds geps that "if the
getelementptr has any non-zero indices[...] [t]he base pointer has an in
bounds address of the allocated object that it is based on [and]
[d]uring the successive addition of offsets to the address, the
resulting pointer must remain in bounds of the allocated object at each
step."

If (gep inbounds p, (a + 5)) is translated to (gep [inbounds] (gep p,
a), 5) with p pointing to the beginning of an object and a=-4, as the
example in the comments suggests, that's the case for neither of the
resulting geps. Therefore, we need to clear the inbounds flag for both
geps.

We might want to use ValueTracking to check if a is known to be
non-negative to preserve the inbounds flags.

For the AMDGPU tests with scratch instructions, removing the unsound
inbounds flag means that AMDGPUDAGToDAGISel::isFlatScratchBaseLegal sees
no NUW flag at the pointer add, which prevents generation of scratch
instructions with immediate offsets.

For SWDEV-516125.



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