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[InstCombine] Fold gep of exact unsigned division #82334

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Feb 20, 2024
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[InstCombine] Fold gep of exact unsigned division #82334

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6 changes: 3 additions & 3 deletions llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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());
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6 changes: 2 additions & 4 deletions llvm/test/Transforms/InstCombine/getelementptr.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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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