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[ValueTracking] Return true for AddrSpaceCast in canCreateUndefOrPoison #144686

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[ValueTracking] Return true for AddrSpaceCast in canCreateUndefOrPoison #144686

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b5c9a48
[InstCombine] Don't folder select to or if value argument is user of …
wenju-he Jun 18, 2025
ffff2c3
update LangRef, refine test
wenju-he Jun 19, 2025
3128b33
return true for AddrSpaceCast in canCreateUndefOrPoison, update Attri…
wenju-he Jun 20, 2025
b86394e
update clang tests
wenju-he Jun 20, 2025
b35f28c
revert change to AttributorAttributes
wenju-he Jun 20, 2025
3c42596
Update llvm/test/Transforms/InstCombine/AMDGPU/addrspacecast.ll
wenju-he Jun 20, 2025
7d0d17e
remove 'may' in test comment
wenju-he Jun 23, 2025
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2 changes: 1 addition & 1 deletion clang/test/CodeGenOpenCL/amdgcn-buffer-rsrc-type.cl
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Expand Up @@ -44,7 +44,7 @@ void consumeBufferPtr(__amdgpu_buffer_rsrc_t *p) {
// CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr addrspace(5) [[A]], align 16, !tbaa [[TBAA8:![0-9]+]]
// CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i32 [[TMP0]], 0
// CHECK-NEXT: [[TOBOOL_NOT_I:%.*]] = icmp eq ptr addrspace(5) [[A]], addrspacecast (ptr null to ptr addrspace(5))
// CHECK-NEXT: [[OR_COND:%.*]] = or i1 [[TOBOOL_NOT_I]], [[TOBOOL_NOT]]
// CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[TOBOOL_NOT]], i1 true, i1 [[TOBOOL_NOT_I]]
// CHECK-NEXT: br i1 [[OR_COND]], label [[IF_END:%.*]], label [[IF_THEN_I:%.*]]
// CHECK: if.then.i:
// CHECK-NEXT: [[R:%.*]] = getelementptr inbounds nuw i8, ptr addrspace(5) [[A]], i32 16
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2 changes: 1 addition & 1 deletion clang/test/CodeGenOpenCL/as_type.cl
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Expand Up @@ -67,7 +67,7 @@ int3 f8(char16 x) {
return __builtin_astype(x, int3);
}

//CHECK: define{{.*}} spir_func noundef ptr addrspace(1) @addr_cast(ptr noundef readnone captures(ret: address, provenance) %[[x:.*]])
//CHECK: define{{.*}} spir_func ptr addrspace(1) @addr_cast(ptr noundef readnone captures(ret: address, provenance) %[[x:.*]])
//CHECK: %[[cast:.*]] ={{.*}} addrspacecast ptr %[[x]] to ptr addrspace(1)
//CHECK: ret ptr addrspace(1) %[[cast]]
global int* addr_cast(int *x) {
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3 changes: 3 additions & 0 deletions llvm/docs/LangRef.rst
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Expand Up @@ -12627,6 +12627,9 @@ result pointer is dereferenceable, the cast is assumed to be
reversible (i.e. casting the result back to the original address space
should yield the original bit pattern).

Which address space casts are supported depends on the target. Unsupported
address space casts return :ref:`poison <poisonvalues>`.

Example:
""""""""

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2 changes: 2 additions & 0 deletions llvm/lib/Analysis/ValueTracking.cpp
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Expand Up @@ -7483,6 +7483,8 @@ static bool canCreateUndefOrPoison(const Operator *Op, UndefPoisonKind Kind,
case Instruction::FCmp:
case Instruction::GetElementPtr:
return false;
case Instruction::AddrSpaceCast:
return true;
default: {
const auto *CE = dyn_cast<ConstantExpr>(Op);
if (isa<CastInst>(Op) || (CE && CE->isCast()))
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2 changes: 1 addition & 1 deletion llvm/test/Transforms/Attributor/reduced/aapointer_info_map_invalidation.ll
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Expand Up @@ -8,7 +8,7 @@ define amdgpu_kernel void @__omp_offloading_fd00_2c00523__ZN11qmcplusplus7ompBLA
; CHECK-NEXT: [[TMP1:%.*]] = alloca [0 x [0 x float]], i32 0, align 8, addrspace(5)
; CHECK-NEXT: [[TMP2:%.*]] = addrspacecast ptr addrspace(5) [[TMP1]] to ptr
; CHECK-NEXT: store ptr [[TMP2]], ptr addrspace(5) [[TMP1]], align 8
; CHECK-NEXT: [[TMP3:%.*]] = call fastcc i32 @__kmpc_nvptx_parallel_reduce_nowait_v2(ptr nofree noundef readonly align 8 captures(none) dereferenceable_or_null(8) [[TMP2]], i1 noundef false)
; CHECK-NEXT: [[TMP3:%.*]] = call fastcc i32 @__kmpc_nvptx_parallel_reduce_nowait_v2(ptr nofree readonly align 8 captures(none) dereferenceable_or_null(8) [[TMP2]], i1 noundef false)
; CHECK-NEXT: ret void
;
%1 = alloca [0 x [0 x float]], i32 0, align 8, addrspace(5)
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25 changes: 25 additions & 0 deletions llvm/test/Transforms/InstCombine/AMDGPU/addrspacecast.ll
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@@ -0,0 +1,25 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S -mtriple=amdgcn-amd-amdhsa -passes=instcombine %s | FileCheck %s

; Check that `select B, true, C` isn't optimized to `or B, C`,
; because the invalid addrspacecast %asc.shared introduces poison.
define i1 @not_fold_select(ptr addrspace(1) noundef %x) {
; CHECK-LABEL: define i1 @not_fold_select(
; CHECK-SAME: ptr addrspace(1) noundef [[X:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[TMP0:%.*]] = addrspacecast ptr addrspace(1) [[X]] to ptr
; CHECK-NEXT: [[TMP1:%.*]] = tail call i1 @llvm.amdgcn.is.shared(ptr [[TMP0]])
; CHECK-NEXT: [[TMP2:%.*]] = addrspacecast ptr addrspace(1) [[X]] to ptr addrspace(3)
; CHECK-NEXT: [[TMP3:%.*]] = icmp eq ptr addrspace(3) [[TMP2]], null
; CHECK-NEXT: [[NOT_IS_SHARED:%.*]] = xor i1 [[TMP1]], true
; CHECK-NEXT: [[TMP4:%.*]] = select i1 [[NOT_IS_SHARED]], i1 true, i1 [[TMP3]]
; CHECK-NEXT: ret i1 [[TMP4]]
;
entry:
%asc.flat = addrspacecast ptr addrspace(1) %x to ptr
%is.shared = tail call i1 @llvm.amdgcn.is.shared(ptr %asc.flat)
%asc.shared = addrspacecast ptr %asc.flat to ptr addrspace(3)
%shared.addr = select i1 %is.shared, ptr addrspace(3) %asc.shared, ptr addrspace(3) null
%result = icmp eq ptr addrspace(3) %shared.addr, null
ret i1 %result
}