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[InstCombine] Remove one-use restriction on icmp of gep fold #76730

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Merged
merged 3 commits into from
Feb 9, 2024
Merged

[InstCombine] Remove one-use restriction on icmp of gep fold #76730

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bd9ca79
[InstCombine] Remove one-use restriction on icmp of gep fold
nikic Dec 8, 2023
efe5e2d
Don't recreate GEP if it already has i8 type
nikic Jan 3, 2024
a8994d2
add insert point guard
nikic Jan 3, 2024
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30 changes: 23 additions & 7 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -813,14 +813,30 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
}
}

// Only lower this if the icmp is the only user of the GEP or if we expect
// the result to fold to a constant!
if ((GEPsInBounds || CmpInst::isEquality(Cond)) &&
(GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
(GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse())) {
if (GEPsInBounds || CmpInst::isEquality(Cond)) {
auto EmitGEPOffsetAndRewrite = [&](GEPOperator *GEP) {
IRBuilderBase::InsertPointGuard Guard(Builder);
auto *Inst = dyn_cast<Instruction>(GEP);
if (Inst)
Builder.SetInsertPoint(Inst);

Value *Offset = EmitGEPOffset(GEP);
// If a non-trivial GEP has other uses, rewrite it to avoid duplicating
// the offset arithmetic.
if (Inst && !GEP->hasOneUse() && !GEP->hasAllConstantIndices() &&
!GEP->getSourceElementType()->isIntegerTy(8)) {
replaceInstUsesWith(*Inst,
Builder.CreateGEP(Builder.getInt8Ty(),
GEP->getPointerOperand(),
Offset, "", GEPsInBounds));
eraseInstFromFunction(*Inst);
}
return Offset;
};

// ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
Value *L = EmitGEPOffset(GEPLHS);
Value *R = EmitGEPOffset(GEPRHS);
Value *L = EmitGEPOffsetAndRewrite(GEPLHS);
Value *R = EmitGEPOffsetAndRewrite(GEPRHS);
return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
}
}
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4 changes: 2 additions & 2 deletions llvm/test/Transforms/InstCombine/icmp-custom-dl.ll
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Expand Up @@ -40,8 +40,8 @@ define i1 @test59_as1(ptr addrspace(1) %foo) {
define i1 @test60(ptr %foo, i64 %i, i64 %j) {
; CHECK-LABEL: @test60(
; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[I:%.*]] to i32
; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i32
; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i32 [[TMP1]], 2
; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i32
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[GEP1_IDX]], [[TMP2]]
; CHECK-NEXT: ret i1 [[CMP]]
;
Expand All @@ -54,8 +54,8 @@ define i1 @test60(ptr %foo, i64 %i, i64 %j) {
define i1 @test60_as1(ptr addrspace(1) %foo, i64 %i, i64 %j) {
; CHECK-LABEL: @test60_as1(
; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[I:%.*]] to i16
; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i16
; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i16 [[TMP1]], 2
; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i16 [[GEP1_IDX]], [[TMP2]]
; CHECK-NEXT: ret i1 [[CMP]]
;
Expand Down
17 changes: 10 additions & 7 deletions llvm/test/Transforms/InstCombine/icmp-gep.ll
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Expand Up @@ -313,8 +313,8 @@ define i1 @test_gep_eq_no_inbounds(ptr %foo, i64 %i, i64 %j) {
define i1 @test60_as1(ptr addrspace(1) %foo, i64 %i, i64 %j) {
; CHECK-LABEL: @test60_as1(
; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[I:%.*]] to i16
; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i16
; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i16 [[TMP1]], 2
; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[J:%.*]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i16 [[GEP1_IDX]], [[TMP2]]
; CHECK-NEXT: ret i1 [[CMP]]
;
Expand Down Expand Up @@ -400,11 +400,13 @@ define i1 @test61_as1(ptr addrspace(1) %foo, i16 %i, i16 %j) {

define i1 @test60_extra_use(ptr %foo, i64 %i, i64 %j) {
; CHECK-LABEL: @test60_extra_use(
; CHECK-NEXT: [[GEP1:%.*]] = getelementptr inbounds i32, ptr [[FOO:%.*]], i64 [[I:%.*]]
; CHECK-NEXT: [[GEP2:%.*]] = getelementptr inbounds i16, ptr [[FOO]], i64 [[J:%.*]]
; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i64 [[I:%.*]], 2
; CHECK-NEXT: [[GEP1:%.*]] = getelementptr inbounds i8, ptr [[FOO:%.*]], i64 [[GEP1_IDX]]
; CHECK-NEXT: [[GEP2_IDX:%.*]] = shl nsw i64 [[J:%.*]], 1
; CHECK-NEXT: [[GEP2:%.*]] = getelementptr inbounds i8, ptr [[FOO]], i64 [[GEP2_IDX]]
; CHECK-NEXT: call void @use(ptr [[GEP1]])
; CHECK-NEXT: call void @use(ptr [[GEP2]])
; CHECK-NEXT: [[CMP:%.*]] = icmp ult ptr [[GEP1]], [[GEP2]]
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i64 [[GEP1_IDX]], [[GEP2_IDX]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%gep1 = getelementptr inbounds i32, ptr %foo, i64 %i
Expand Down Expand Up @@ -446,13 +448,14 @@ define i1 @test60_extra_use_const_operands_no_inbounds(ptr %foo, i64 %i, i64 %j)

define void @test60_extra_use_fold(ptr %foo, i64 %start.idx, i64 %end.offset) {
; CHECK-LABEL: @test60_extra_use_fold(
; CHECK-NEXT: [[GEP1:%.*]] = getelementptr inbounds i32, ptr [[FOO:%.*]], i64 [[START_IDX:%.*]]
; CHECK-NEXT: [[GEP1_IDX:%.*]] = shl nsw i64 [[START_IDX:%.*]], 2
; CHECK-NEXT: [[GEP1:%.*]] = getelementptr inbounds i8, ptr [[FOO:%.*]], i64 [[GEP1_IDX]]
; CHECK-NEXT: [[GEP2:%.*]] = getelementptr inbounds i8, ptr [[FOO]], i64 [[END_OFFSET:%.*]]
; CHECK-NEXT: call void @use(ptr [[GEP1]])
; CHECK-NEXT: call void @use(ptr [[GEP2]])
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq ptr [[GEP1]], [[GEP2]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i64 [[GEP1_IDX]], [[END_OFFSET]]
; CHECK-NEXT: call void @use.i1(i1 [[CMP1]])
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult ptr [[GEP1]], [[GEP2]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i64 [[GEP1_IDX]], [[END_OFFSET]]
; CHECK-NEXT: call void @use.i1(i1 [[CMP2]])
; CHECK-NEXT: ret void
;
Expand Down