[all-commits] [llvm/llvm-project] 9d570d: [ValueTracking] Return true for AddrSpaceCast in c...

[Wenju He via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 9d570d568b37249ddcff8319c5965c4bdc4f7ca2
      https://github.com/llvm/llvm-project/commit/9d570d568b37249ddcff8319c5965c4bdc4f7ca2
  Author: Wenju He <wenju.he at intel.com>
  Date:   2025-06-24 (Tue, 24 Jun 2025)

  Changed paths:
    M clang/test/CodeGenOpenCL/amdgcn-buffer-rsrc-type.cl
    M clang/test/CodeGenOpenCL/as_type.cl
    M llvm/docs/LangRef.rst
    M llvm/lib/Analysis/ValueTracking.cpp
    M llvm/test/Transforms/Attributor/reduced/aapointer_info_map_invalidation.ll
    A llvm/test/Transforms/InstCombine/AMDGPU/addrspacecast.ll

  Log Message:
  -----------
  [ValueTracking] Return true for AddrSpaceCast in canCreateUndefOrPoison (#144686)

In our downstream GPU target, following IR is valid before instcombine
although the second addrspacecast causes UB.
  define i1 @test(ptr addrspace(1) noundef %v) {
    %0 = addrspacecast ptr addrspace(1) %v to ptr addrspace(4)
    %1 = call i32 @llvm.xxxx.isaddr.shared(ptr addrspace(4) %0)
    %2 = icmp eq i32 %1, 0
    %3 = addrspacecast ptr addrspace(4) %0 to ptr addrspace(3)
    %4 = select i1 %2, ptr addrspace(3) null, ptr addrspace(3) %3
    %5 = icmp eq ptr addrspace(3) %4, null
    ret i1 %5
  }
We have a custom optimization that replaces invalid addrspacecast with
poison, and IR is still valid since `select` stops poison propagation.

However, instcombine pass optimizes `select` to `or`:
    %0 = addrspacecast ptr addrspace(1) %v to ptr addrspace(4)
    %1 = call i32 @llvm.xxxx.isaddr.shared(ptr addrspace(4) %0)
    %2 = icmp eq i32 %1, 0
    %3 = addrspacecast ptr addrspace(1) %v to ptr addrspace(3)
    %4 = icmp eq ptr addrspace(3) %3, null
    %5 = or i1 %2, %4
    ret i1 %5
The transform is invalid for our target.

---------

Co-authored-by: Nikita Popov <github at npopov.com>



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