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[InstCombine] Check type compatibility in indexed load fold 

This fold could use a rewrite to an offset-based implementation,
but for now make sure it doesn't crash with opaque pointers.
This commit is contained in:
Nikita Popov 2022-02-11 10:15:17 +01:00
parent 9474c3009e
commit e714b98fff
3 changed files with 62 additions and 23 deletions
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43
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -105,10 +105,14 @@ static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
///
/// If AndCst is non-null, then the loaded value is masked with that constant
/// before doing the comparison. This handles cases like "A[i]&4 == 0".
Instruction *
InstCombinerImpl::foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
GlobalVariable *GV, CmpInst &ICI,
ConstantInt *AndCst) {
Instruction *InstCombinerImpl::foldCmpLoadFromIndexedGlobal(
LoadInst *LI, GetElementPtrInst *GEP, GlobalVariable *GV, CmpInst &ICI,
ConstantInt *AndCst) {
if (LI->isVolatile() || LI->getType() != GEP->getResultElementType() ||
GV->getValueType() != GEP->getSourceElementType() ||
!GV->isConstant() || !GV->hasDefinitiveInitializer())
return nullptr;
Constant *Init = GV->getInitializer();
if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
return nullptr;
@ -1865,15 +1869,13 @@ Instruction *InstCombinerImpl::foldICmpAndConstant(ICmpInst &Cmp,
// Try to optimize things like "A[i] & 42 == 0" to index computations.
Value *X = And->getOperand(0);
Value *Y = And->getOperand(1);
if (auto *LI = dyn_cast<LoadInst>(X))
if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
!LI->isVolatile() && isa<ConstantInt>(Y)) {
ConstantInt *C2 = cast<ConstantInt>(Y);
if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, Cmp, C2))
if (auto *C2 = dyn_cast<ConstantInt>(Y))
if (auto *LI = dyn_cast<LoadInst>(X))
if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
if (Instruction *Res =
foldCmpLoadFromIndexedGlobal(LI, GEP, GV, Cmp, C2))
return Res;
}
if (!Cmp.isEquality())
return nullptr;
@ -3476,13 +3478,11 @@ Instruction *InstCombinerImpl::foldICmpInstWithConstantNotInt(ICmpInst &I) {
case Instruction::Load:
// Try to optimize things like "A[i] > 4" to index computations.
if (GetElementPtrInst *GEP =
dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
dyn_cast<GetElementPtrInst>(LHSI->getOperand(0)))
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
!cast<LoadInst>(LHSI)->isVolatile())
if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
return Res;
}
if (Instruction *Res =
foldCmpLoadFromIndexedGlobal(cast<LoadInst>(LHSI), GEP, GV, I))
return Res;
break;
}
@ -6632,10 +6632,9 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
case Instruction::Load:
if (auto *GEP = dyn_cast<GetElementPtrInst>(LHSI->getOperand(0)))
if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
!cast<LoadInst>(LHSI)->isVolatile())
if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
return Res;
if (Instruction *Res = foldCmpLoadFromIndexedGlobal(
cast<LoadInst>(LHSI), GEP, GV, I))
return Res;
break;
}
}

3
llvm/lib/Transforms/InstCombine/InstCombineInternal.h
View File

@ -652,7 +652,8 @@ public:
ICmpInst::Predicate Cond, Instruction &I);
Instruction *foldAllocaCmp(ICmpInst &ICI, const AllocaInst *Alloca,
const Value *Other);
Instruction *foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
Instruction *foldCmpLoadFromIndexedGlobal(LoadInst *LI,
GetElementPtrInst *GEP,
GlobalVariable *GV, CmpInst &ICI,
ConstantInt *AndCst = nullptr);
Instruction *foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,

39
llvm/test/Transforms/InstCombine/opaque-ptr.ll
View File

@ -305,3 +305,42 @@ define i1 @cmp_gep_same_base_different_type(ptr %ptr, i64 %idx1, i64 %idx2) {
%cmp = icmp ult ptr %gep1, %gep2
ret i1 %cmp
}
@ary = constant [4 x i8] [i8 1, i8 2, i8 3, i8 4]
define i1 @cmp_load_gep_global(i64 %idx) {
; CHECK-LABEL: @cmp_load_gep_global(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[IDX:%.*]], 2
; CHECK-NEXT: ret i1 [[CMP]]
;
%gep = getelementptr [4 x i8], ptr @ary, i64 0, i64 %idx
%load = load i8, ptr %gep
%cmp = icmp eq i8 %load, 3
ret i1 %cmp
}
define i1 @cmp_load_gep_global_different_load_type(i64 %idx) {
; CHECK-LABEL: @cmp_load_gep_global_different_load_type(
; CHECK-NEXT: [[GEP:%.*]] = getelementptr [4 x i8], ptr @ary, i64 0, i64 [[IDX:%.*]]
; CHECK-NEXT: [[LOAD:%.*]] = load i16, ptr [[GEP]], align 2
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i16 [[LOAD]], 3
; CHECK-NEXT: ret i1 [[CMP]]
;
%gep = getelementptr [4 x i8], ptr @ary, i64 0, i64 %idx
%load = load i16, ptr %gep
%cmp = icmp eq i16 %load, 3
ret i1 %cmp
}
define i1 @cmp_load_gep_global_different_gep_type(i64 %idx) {
; CHECK-LABEL: @cmp_load_gep_global_different_gep_type(
; CHECK-NEXT: [[GEP:%.*]] = getelementptr [4 x i16], ptr @ary, i64 0, i64 [[IDX:%.*]]
; CHECK-NEXT: [[LOAD:%.*]] = load i16, ptr [[GEP]], align 2
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i16 [[LOAD]], 3
; CHECK-NEXT: ret i1 [[CMP]]
;
%gep = getelementptr [4 x i16], ptr @ary, i64 0, i64 %idx
%load = load i16, ptr %gep
%cmp = icmp eq i16 %load, 3
ret i1 %cmp
}