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[PowerPC] Bail out of redundant LI elimination on an implicit kill
The transformation currently does not differentiate between explicit and implicit kills. However, it is not valid to later simply clear an implicit kill flag since the kill could be due to a call or return. Fixes: https://bugs.llvm.org/show_bug.cgi?id=45374
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‎llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp

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@@ -109,6 +109,16 @@ namespace {
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// Track the operand that kill Reg. We would unset the kill flag of
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// the operand if there is a following redundant load immediate.
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int KillIdx = AfterBBI->findRegisterUseOperandIdx(Reg, true, TRI);
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// We can't just clear implicit kills, so if we encounter one, stop
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// looking further.
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if (KillIdx != -1 && AfterBBI->getOperand(KillIdx).isImplicit()) {
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LLVM_DEBUG(dbgs()
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<< "Encountered an implicit kill, cannot proceed: ");
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LLVM_DEBUG(AfterBBI->dump());
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break;
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}
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if (KillIdx != -1) {
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assert(!DeadOrKillToUnset && "Shouldn't kill same register twice");
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DeadOrKillToUnset = &AfterBBI->getOperand(KillIdx);

‎llvm/test/CodeGen/PowerPC/remove-redundant-li-skip-imp-kill.mir

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# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
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# RUN: llc -mcpu=pwr9 -mtriple=powerpc64le-unknown-unknown -run-pass \
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# RUN: ppc-pre-emit-peephole %s -o - | FileCheck %s
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--- |
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; ModuleID = 'a.ll'
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source_filename = "a.ll"
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target datalayout = "e-m:e-i64:64-n32:64"
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; Function Attrs: nounwind
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define dso_local signext i32 @b(i32 signext %a, i32* nocapture %b) local_unnamed_addr #0 {
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entry:
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%call = tail call signext i32 @g(i32 signext %a)
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store i32 %call, i32* %b, align 4
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%call1 = tail call signext i32 @g(i32 signext %a)
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ret i32 %call1
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}
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; Function Attrs: nounwind
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declare signext i32 @g(i32 signext) local_unnamed_addr #0
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; Function Attrs: nounwind
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declare void @llvm.stackprotector(i8*, i8**) #0
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attributes #0 = { nounwind }
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...
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---
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name: b
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alignment: 16
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exposesReturnsTwice: false
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legalized: false
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regBankSelected: false
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selected: false
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failedISel: false
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tracksRegLiveness: true
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hasWinCFI: false
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registers: []
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liveins:
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- { reg: '$x3', virtual-reg: '' }
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- { reg: '$x4', virtual-reg: '' }
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frameInfo:
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isFrameAddressTaken: false
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isReturnAddressTaken: false
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hasStackMap: false
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hasPatchPoint: false
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stackSize: 64
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offsetAdjustment: 0
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maxAlignment: 1
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adjustsStack: true
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hasCalls: true
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stackProtector: ''
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maxCallFrameSize: 32
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cvBytesOfCalleeSavedRegisters: 0
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hasOpaqueSPAdjustment: false
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hasVAStart: false
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hasMustTailInVarArgFunc: false
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localFrameSize: 0
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savePoint: ''
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restorePoint: ''
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fixedStack:
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- { id: 0, type: spill-slot, offset: -80, size: 8, alignment: 16, stack-id: default,
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callee-saved-register: '$x30', callee-saved-restored: true, debug-info-variable: '',
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debug-info-expression: '', debug-info-___location: '' }
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- { id: 1, type: spill-slot, offset: -88, size: 8, alignment: 8, stack-id: default,
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callee-saved-register: '$x29', callee-saved-restored: true, debug-info-variable: '',
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debug-info-expression: '', debug-info-___location: '' }
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stack: []
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callSites: []
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constants: []
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machineFunctionInfo: {}
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body: |
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bb.0.entry:
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liveins: $x3, $x4, $x29, $x30
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; CHECK-LABEL: name: b
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; CHECK: liveins: $x3, $x4, $x29, $x30
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; CHECK: $x0 = MFLR8 implicit $lr8
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; CHECK: STD killed $x29, -24, $x1 :: (store 8 into %fixed-stack.0)
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; CHECK: STD killed $x30, -16, $x1 :: (store 8 into %fixed-stack.1, align 16)
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; CHECK: STD killed $x0, 16, $x1
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; CHECK: $x1 = STDU $x1, -64, $x1
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; CHECK: $x30 = OR8 killed $x4, $x4
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; CHECK: dead $r4 = LI 10, implicit-def $x4
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; CHECK: $x29 = OR8 $x3, $x3
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; CHECK: BL8_NOP @g, csr_ppc64_r2_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit killed $x4, implicit $x2, implicit-def $r1, implicit-def $x3
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; CHECK: STW8 killed renamable $x3, 0, killed renamable $x30 :: (store 4 into %ir.b)
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; CHECK: $x3 = OR8 killed $x29, $x29
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; CHECK: BL8_NOP @g, csr_ppc64_r2_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit $x2, implicit-def $r1, implicit-def $x3
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; CHECK: $x1 = ADDI8 $x1, 64
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; CHECK: $x0 = LD 16, $x1
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; CHECK: $x30 = LD -16, $x1 :: (load 8 from %fixed-stack.1, align 16)
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; CHECK: $x29 = LD -24, $x1 :: (load 8 from %fixed-stack.0)
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; CHECK: MTLR8 killed $x0, implicit-def $lr8
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; CHECK: BLR8 implicit $lr8, implicit $rm, implicit killed $x3
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$x0 = MFLR8 implicit $lr8
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STD killed $x29, -24, $x1 :: (store 8 into %fixed-stack.1)
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STD killed $x30, -16, $x1 :: (store 8 into %fixed-stack.0, align 16)
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STD killed $x0, 16, $x1
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$x1 = STDU $x1, -64, $x1
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$x30 = OR8 killed $x4, $x4
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dead $r4 = LI 10, implicit-def $x4
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$x29 = OR8 $x3, $x3
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BL8_NOP @g, csr_ppc64_r2_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit killed $x4, implicit $x2, implicit-def $r1, implicit-def $x3
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STW8 killed renamable $x3, 0, killed renamable $x30 :: (store 4 into %ir.b)
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$x3 = OR8 killed $x29, $x29
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BL8_NOP @g, csr_ppc64_r2_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit $x2, implicit-def $r1, implicit-def $x3
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$x1 = ADDI8 $x1, 64
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$x0 = LD 16, $x1
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$x30 = LD -16, $x1 :: (load 8 from %fixed-stack.0, align 16)
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$x29 = LD -24, $x1 :: (load 8 from %fixed-stack.1)
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MTLR8 killed $x0, implicit-def $lr8
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BLR8 implicit $lr8, implicit $rm, implicit killed $x3
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...

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