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[SelectOpt] Fix incorrect IR for SUB when comparison dependent operand is first #119362

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Merged
merged 1 commit into from
Dec 10, 2024
Merged

[SelectOpt] Fix incorrect IR for SUB when comparison dependent operand is first #119362

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7 changes: 6 additions & 1 deletion llvm/lib/CodeGen/SelectOptimize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -806,7 +806,12 @@ void SelectOptimizeImpl::collectSelectGroups(BasicBlock &BB,
break;
}

for (unsigned Idx = 0; Idx < 2; Idx++) {
// Iterate through operands and find dependant on recognised sign
// extending auxiliary select-like instructions. The operand index does
// not matter for Add and Or. However, for Sub, we can only safely
// transform when the operand is second.
unsigned Idx = BO->getOpcode() == Instruction::Sub ? 1 : 0;
for (; Idx < 2; Idx++) {
auto *Op = BO->getOperand(Idx);
auto It = SelectInfo.find(Op);
if (It != SelectInfo.end() && It->second.IsAuxiliary) {
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14 changes: 4 additions & 10 deletions llvm/test/CodeGen/AArch64/selectopt-cast.ll
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Expand Up @@ -427,22 +427,16 @@ define void @test_sub_zext_first_op(ptr %dst, ptr %src, i64 %j.start, i64 %p, i6
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV1:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[SELECT_END:%.*]] ]
; CHECK-NEXT: [[J:%.*]] = phi i64 [ [[J_START:%.*]], [[ENTRY]] ], [ [[J_NEXT:%.*]], [[SELECT_END]] ]
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[I_START:%.*]], [[ENTRY]] ], [ [[J_NEXT]], [[SELECT_END]] ]
; CHECK-NEXT: [[IV1:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[J:%.*]] = phi i64 [ [[J_START:%.*]], [[ENTRY]] ], [ [[J_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[I_START:%.*]], [[ENTRY]] ], [ [[J_NEXT]], [[LOOP]] ]
; CHECK-NEXT: [[GEP_DST:%.*]] = getelementptr inbounds ptr, ptr [[DST:%.*]], i64 [[IV]]
; CHECK-NEXT: [[L_I:%.*]] = load ptr, ptr [[GEP_DST]], align 8
; CHECK-NEXT: [[GEP_J:%.*]] = getelementptr inbounds ptr, ptr [[DST]], i64 [[J]]
; CHECK-NEXT: [[L_J:%.*]] = load ptr, ptr [[GEP_J]], align 8
; CHECK-NEXT: [[CMP3:%.*]] = icmp ult ptr [[L_I]], [[L_J]]
; CHECK-NEXT: [[DEC:%.*]] = zext i1 [[CMP3]] to i64
; CHECK-NEXT: [[CMP3_FROZEN:%.*]] = freeze i1 [[CMP3]]
; CHECK-NEXT: br i1 [[CMP3_FROZEN]], label [[SELECT_TRUE_SINK:%.*]], label [[SELECT_END]]
; CHECK: select.true.sink:
; CHECK-NEXT: [[TMP0:%.*]] = sub nsw i64 1, [[J]]
; CHECK-NEXT: br label [[SELECT_END]]
; CHECK: select.end:
; CHECK-NEXT: [[J_NEXT]] = phi i64 [ [[TMP0]], [[SELECT_TRUE_SINK]] ], [ [[J]], [[LOOP]] ]
; CHECK-NEXT: [[J_NEXT]] = sub nsw i64 [[DEC]], [[J]]
; CHECK-NEXT: [[GEP_DST1:%.*]] = getelementptr inbounds ptr, ptr [[DST1:%.*]], i64 [[IV1]]
; CHECK-NEXT: store i64 [[J_NEXT]], ptr [[GEP_DST1]], align 8
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV1]], 1
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