AArch64: be careful of large immediates when optimising cmps.
llvm-svn: 243492
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@ -154,11 +154,18 @@ MachineInstr *AArch64ConditionOptimizer::findSuitableCompare(
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// cmn is an alias for adds with a dead destination register.
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case AArch64::ADDSWri:
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case AArch64::ADDSXri:
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if (MRI->use_empty(I->getOperand(0).getReg()))
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return I;
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if (!I->getOperand(2).isImm()) {
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DEBUG(dbgs() << "Immediate of cmp is symbolic, " << *I << '\n');
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return nullptr;
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} else if (I->getOperand(2).getImm() << I->getOperand(3).getImm() >=
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0xfff) {
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DEBUG(dbgs() << "Immediate of cmp may be out of range, " << *I << '\n');
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return nullptr;
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} else if (!MRI->use_empty(I->getOperand(0).getReg())) {
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DEBUG(dbgs() << "Destination of cmp is not dead, " << *I << '\n');
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return nullptr;
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}
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return I;
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// Prevent false positive case like:
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// cmp w19, #0
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@ -403,6 +403,32 @@ return: ; preds = %land.lhs.true, %con
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ret i32 %retval.0
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}
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define void @cmp_shifted(i32 %in, i32 %lhs, i32 %rhs) {
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; CHECK-LABEL: cmp_shifted:
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; CHECK: cmp w0, #1
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; [...]
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; CHECK: cmp w0, #2, lsl #12
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%tst_low = icmp sgt i32 %in, 0
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br i1 %tst_low, label %true, label %false
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true:
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call i32 @zoo(i32 128)
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ret void
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false:
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%tst = icmp sgt i32 %in, 8191
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br i1 %tst, label %truer, label %falser
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truer:
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call i32 @zoo(i32 42)
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ret void
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falser:
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call i32 @zoo(i32 1)
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ret void
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}
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declare i32 @zoo(i32)
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declare double @yoo(i32)
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