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[ConstraintElimination] Decompose GEP with arbitrary offsets. 

This patch decomposes `GEP %x, %offset` as  0 + 1 * %x + 1 * %off.
This commit is contained in:
Florian Hahn 2020-11-18 11:45:26 +00:00
parent dfe67f450e
commit 7fa14a7c69
No known key found for this signature in database
GPG Key ID: 61D7554B5CECDC0D
2 changed files with 12 additions and 8 deletions
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16
llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
View File

@ -50,12 +50,16 @@ static SmallVector<std::pair<int64_t, Value *>, 4> decompose(Value *V) {
return {{CI->getSExtValue(), nullptr}};
}
auto *GEP = dyn_cast<GetElementPtrInst>(V);
if (GEP && GEP->getNumOperands() == 2 &&
isa<ConstantInt>(GEP->getOperand(GEP->getNumOperands() - 1))) {
return {{cast<ConstantInt>(GEP->getOperand(GEP->getNumOperands() - 1))
->getSExtValue(),
nullptr},
{1, GEP->getPointerOperand()}};
if (GEP && GEP->getNumOperands() == 2) {
if (isa<ConstantInt>(GEP->getOperand(GEP->getNumOperands() - 1))) {
return {{cast<ConstantInt>(GEP->getOperand(GEP->getNumOperands() - 1))
->getSExtValue(),
nullptr},
{1, GEP->getPointerOperand()}};
}
return {{0, nullptr},
{1, GEP->getPointerOperand()},
{1, GEP->getOperand(GEP->getNumOperands() - 1)}};
}
Value *Op0;

4
llvm/test/Transforms/ConstraintElimination/geps.ll
View File

@ -336,7 +336,7 @@ define void @test.not.uge.uge.nonconst(i8* %start, i8* %low, i8* %high, i64 %off
; CHECK: if.then:
; CHECK-NEXT: [[START_OFF_2:%.*]] = getelementptr inbounds i8, i8* [[START]], i64 [[OFF]]
; CHECK-NEXT: [[T_0:%.*]] = icmp uge i8* [[START_OFF_2]], [[HIGH]]
; CHECK-NEXT: call void @use(i1 [[T_0]])
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: ret void
; CHECK: if.end:
; CHECK-NEXT: [[START_1:%.*]] = getelementptr inbounds i8, i8* [[START]], i64 1
@ -344,7 +344,7 @@ define void @test.not.uge.uge.nonconst(i8* %start, i8* %low, i8* %high, i64 %off
; CHECK-NEXT: call void @use(i1 [[C_0]])
; CHECK-NEXT: [[START_OFF:%.*]] = getelementptr inbounds i8, i8* [[START]], i64 [[OFF]]
; CHECK-NEXT: [[F_0:%.*]] = icmp uge i8* [[START_OFF]], [[HIGH]]
; CHECK-NEXT: call void @use(i1 [[F_0]])
; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: ret void
;
entry: