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[SimplifyCFG] Remove limitation on sinking of load/store of alloca #104788

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Merged
merged 1 commit into from
Aug 26, 2024
Merged

[SimplifyCFG] Remove limitation on sinking of load/store of alloca #104788

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19 changes: 4 additions & 15 deletions llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2031,21 +2031,10 @@ static bool canSinkInstructions(
return I->getOperand(OI) == I0->getOperand(OI);
};
if (!all_of(Insts, SameAsI0)) {
// Because SROA historically couldn't handle speculating stores of
// selects, we try not to sink loads, stores or lifetime markers of
// allocas when we'd have to create a PHI for the address operand.
// TODO: SROA supports speculation for loads and stores now -- remove
// this hack?
if (isa<StoreInst>(I0) && OI == 1 &&
any_of(Insts, [](const Instruction *I) {
return isa<AllocaInst>(I->getOperand(1)->stripPointerCasts());
}))
return false;
if (isa<LoadInst>(I0) && OI == 0 &&
any_of(Insts, [](const Instruction *I) {
return isa<AllocaInst>(I->getOperand(0)->stripPointerCasts());
}))
return false;
// SROA can't speculate lifetime markers of selects/phis, and the
// backend may handle such lifetimes incorrectly as well (#104776).
// Don't sink lifetimes if it would introduce a phi on the pointer
// argument.
if (isLifeTimeMarker(I0) && OI == 1 &&
any_of(Insts, [](const Instruction *I) {
return isa<AllocaInst>(I->getOperand(1)->stripPointerCasts());
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21 changes: 6 additions & 15 deletions llvm/test/Transforms/SimplifyCFG/X86/sink-common-code.ll
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Expand Up @@ -801,14 +801,8 @@ define i32 @test_pr30188(i1 zeroext %flag, i32 %x) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[Y:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[Z:%.*]] = alloca i32, align 4
; CHECK-NEXT: br i1 [[FLAG:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: store i32 [[X:%.*]], ptr [[Y]], align 4
; CHECK-NEXT: br label [[IF_END:%.*]]
; CHECK: if.else:
; CHECK-NEXT: store i32 [[X]], ptr [[Z]], align 4
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[Y_Z:%.*]] = select i1 [[FLAG:%.*]], ptr [[Y]], ptr [[Z]]
; CHECK-NEXT: store i32 [[X:%.*]], ptr [[Y_Z]], align 4
; CHECK-NEXT: ret i32 1
;
entry:
Expand All @@ -834,17 +828,14 @@ define i32 @test_pr30188a(i1 zeroext %flag, i32 %x) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[Y:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[Z:%.*]] = alloca i32, align 4
; CHECK-NEXT: br i1 [[FLAG:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK-NEXT: br i1 [[FLAG:%.*]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
; CHECK: if.then:
; CHECK-NEXT: call void @g()
; CHECK-NEXT: [[ONE:%.*]] = load i32, ptr [[Y]], align 4
; CHECK-NEXT: br label [[IF_END:%.*]]
; CHECK: if.else:
; CHECK-NEXT: [[THREE:%.*]] = load i32, ptr [[Z]], align 4
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[THREE_SINK:%.*]] = phi i32 [ [[THREE]], [[IF_ELSE]] ], [ [[ONE]], [[IF_THEN]] ]
; CHECK-NEXT: [[FOUR:%.*]] = add i32 [[THREE_SINK]], 2
; CHECK-NEXT: [[Z_SINK:%.*]] = phi ptr [ [[Y]], [[IF_THEN]] ], [ [[Z]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[THREE:%.*]] = load i32, ptr [[Z_SINK]], align 4
; CHECK-NEXT: [[FOUR:%.*]] = add i32 [[THREE]], 2
; CHECK-NEXT: store i32 [[FOUR]], ptr [[Y]], align 4
; CHECK-NEXT: ret i32 1
;
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