[InstCombine] Fold gep of exact unsigned division #82334
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Extend the transform added in llvm#76458 to also handle unsigned division. X exact/ Y * Y == X holds independently of whether the division is signed or unsigned. Proofs: https://alive2.llvm.org/ce/z/wFd5Ec
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@llvm/pr-subscribers-llvm-transforms Author: Nikita Popov (nikic) ChangesExtend the transform added in #76458 to also handle unsigned division. X exact/ Y * Y == X holds independently of whether the division is signed or unsigned. Proofs: https://alive2.llvm.org/ce/z/wFd5Ec Full diff: https://github.com/llvm/llvm-project/pull/82334.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 7450f39c1e7641..4dbb79f7bef887 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2615,10 +2615,10 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *V;
if ((has_single_bit(TyAllocSize) &&
match(GEP.getOperand(1),
- m_Exact(m_AShr(m_Value(V),
- m_SpecificInt(countr_zero(TyAllocSize)))))) ||
+ m_Exact(m_Shr(m_Value(V),
+ m_SpecificInt(countr_zero(TyAllocSize)))))) ||
match(GEP.getOperand(1),
- m_Exact(m_SDiv(m_Value(V), m_SpecificInt(TyAllocSize))))) {
+ m_Exact(m_IDiv(m_Value(V), m_SpecificInt(TyAllocSize))))) {
GetElementPtrInst *NewGEP = GetElementPtrInst::Create(
Builder.getInt8Ty(), GEP.getPointerOperand(), V);
NewGEP->setIsInBounds(GEP.isInBounds());
diff --git a/llvm/test/Transforms/InstCombine/getelementptr.ll b/llvm/test/Transforms/InstCombine/getelementptr.ll
index a9c619f3fddd05..04b0c196ab5108 100644
--- a/llvm/test/Transforms/InstCombine/getelementptr.ll
+++ b/llvm/test/Transforms/InstCombine/getelementptr.ll
@@ -1477,8 +1477,7 @@ define ptr @gep_sdiv(ptr %p, i64 %off) {
define ptr @gep_udiv(ptr %p, i64 %off) {
; CHECK-LABEL: @gep_udiv(
-; CHECK-NEXT: [[INDEX:%.*]] = udiv exact i64 [[OFF:%.*]], 7
-; CHECK-NEXT: [[PTR:%.*]] = getelementptr [[STRUCT_C:%.*]], ptr [[P:%.*]], i64 [[INDEX]]
+; CHECK-NEXT: [[PTR:%.*]] = getelementptr i8, ptr [[P:%.*]], i64 [[OFF:%.*]]
; CHECK-NEXT: ret ptr [[PTR]]
;
%index = udiv exact i64 %off, 7
@@ -1518,8 +1517,7 @@ define ptr @gep_ashr(ptr %p, i64 %off) {
define ptr @gep_lshr(ptr %p, i64 %off) {
; CHECK-LABEL: @gep_lshr(
-; CHECK-NEXT: [[INDEX:%.*]] = lshr exact i64 [[OFF:%.*]], 2
-; CHECK-NEXT: [[PTR:%.*]] = getelementptr i32, ptr [[P:%.*]], i64 [[INDEX]]
+; CHECK-NEXT: [[PTR:%.*]] = getelementptr i8, ptr [[P:%.*]], i64 [[OFF:%.*]]
; CHECK-NEXT: ret ptr [[PTR]]
;
%index = lshr exact i64 %off, 2
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Extend the transform added in llvm#76458 to also handle unsigned division. X exact/ Y * Y == X holds independently of whether the division is signed or unsigned. Proofs: https://alive2.llvm.org/ce/z/wFd5Ec (cherry picked from commit 26d4afc)
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/pull-request #82347 |
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Extend the transform added in #76458 to also handle unsigned division. X exact/ Y * Y == X holds independently of whether the division is signed or unsigned.
Proofs: https://alive2.llvm.org/ce/z/wFd5Ec