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[GVNHoist] Preserve optimization hints which agree 

If we have optimization hints with agree with each other along different
paths, preserve them.

llvm-svn: 276248
This commit is contained in:
David Majnemer 2016-07-21 07:16:26 +00:00
parent 903eefd1f2
commit 825e4ab9e3
2 changed files with 61 additions and 3 deletions
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20
llvm/lib/Transforms/Scalar/GVNHoist.cpp
View File

@ -574,7 +574,8 @@ public:
llvm_unreachable("Both I and J must be from same BB");
}
bool makeOperandsAvailable(Instruction *Repl, BasicBlock *HoistPt) const {
bool makeOperandsAvailable(Instruction *Repl, BasicBlock *HoistPt,
const SmallVecInsn &InstructionsToHoist) const {
// Check whether the GEP of a ld/st can be synthesized at HoistPt.
GetElementPtrInst *Gep = nullptr;
Instruction *Val = nullptr;
@ -606,7 +607,15 @@ public:
// Conservatively discard any optimization hints, they may differ on the
// other paths.
ClonedGep->dropUnknownNonDebugMetadata();
ClonedGep->clearSubclassOptionalData();
for (const Instruction *OtherInst : InstructionsToHoist) {
const GetElementPtrInst *OtherGep;
if (auto *OtherLd = dyn_cast<LoadInst>(OtherInst))
OtherGep = cast<GetElementPtrInst>(OtherLd->getPointerOperand());
else
OtherGep = cast<GetElementPtrInst>(
cast<StoreInst>(OtherInst)->getPointerOperand());
ClonedGep->intersectOptionalDataWith(OtherGep);
}
Repl->replaceUsesOfWith(Gep, ClonedGep);
// Also copy Val.
@ -616,6 +625,11 @@ public:
// Conservatively discard any optimization hints, they may differ on the
// other paths.
ClonedVal->dropUnknownNonDebugMetadata();
for (const Instruction *OtherInst : InstructionsToHoist) {
const auto *OtherVal =
cast<Instruction>(cast<StoreInst>(OtherInst)->getValueOperand());
ClonedVal->intersectOptionalDataWith(OtherVal);
}
ClonedVal->clearSubclassOptionalData();
Repl->replaceUsesOfWith(Val, ClonedVal);
}
@ -652,7 +666,7 @@ public:
// The order in which hoistings are done may influence the availability
// of operands.
if (!allOperandsAvailable(Repl, HoistPt) &&
!makeOperandsAvailable(Repl, HoistPt))
!makeOperandsAvailable(Repl, HoistPt, InstructionsToHoist))
continue;
Repl->moveBefore(HoistPt->getTerminator());
// TBAA may differ on one of the other paths, we need to get rid of

44
llvm/test/Transforms/GVN/hoist-md.ll
View File

@ -21,6 +21,50 @@ if.end: ; preds = %if.else, %if.then
; CHECK: store i32 2, i32* %x, align 4
; CHECK-NEXT: br i1 %b
define void @test2(i1 %b, i32* %x) {
entry:
br i1 %b, label %if.then, label %if.else
if.then: ; preds = %entry
%gep1 = getelementptr inbounds i32, i32* %x, i64 1
store i32 2, i32* %gep1, align 4, !tbaa !1
br label %if.end
if.else: ; preds = %entry
%gep2 = getelementptr inbounds i32, i32* %x, i64 1
store i32 2, i32* %gep2, align 4, !tbaa !5
br label %if.end
if.end: ; preds = %if.else, %if.then
ret void
}
; CHECK-LABEL: define void @test2(
; CHECK: %[[gep:.*]] = getelementptr inbounds i32, i32* %x, i64 1
; CHECK: store i32 2, i32* %[[gep]], align 4
; CHECK-NEXT: br i1 %b
define void @test3(i1 %b, i32* %x) {
entry:
br i1 %b, label %if.then, label %if.else
if.then: ; preds = %entry
%gep1 = getelementptr inbounds i32, i32* %x, i64 1
store i32 2, i32* %gep1, align 4, !tbaa !1
br label %if.end
if.else: ; preds = %entry
%gep2 = getelementptr i32, i32* %x, i64 1
store i32 2, i32* %gep2, align 4, !tbaa !5
br label %if.end
if.end: ; preds = %if.else, %if.then
ret void
}
; CHECK-LABEL: define void @test3(
; CHECK: %[[gep:.*]] = getelementptr i32, i32* %x, i64 1
; CHECK: store i32 2, i32* %[[gep]], align 4
; CHECK-NEXT: br i1 %b
!1 = !{!2, !2, i64 0}
!2 = !{!"int", !3, i64 0}
!3 = !{!"omnipotent char", !4, i64 0}