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[Statepoint] Treat undef operands less specially
This reverts commit f744390. This is to avoid an assertion if an undef operand appears in a stackmap. This is important to avoid hitting verifier errors when register allocation starts adding undefs in error scenarios. Rather than trying to treat undef operands as special, leave them alone and avoid producing an invalid spill. It would a bit more precise to produce a spill of an undef register here, but that's not exposed through the storeRegToStackSlot API. https://reviews.llvm.org/D122605 This was an alternative to https://reviews.llvm.org/D122582
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lines changed

4 files changed

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lines changed

‎llvm/lib/CodeGen/FixupStatepointCallerSaved.cpp

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Original file line numberDiff line numberDiff line change
@@ -381,8 +381,6 @@ class StatepointState {
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EndIdx = MI.getNumOperands();
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Idx < EndIdx; ++Idx) {
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MachineOperand &MO = MI.getOperand(Idx);
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// Leave `undef` operands as is, StackMaps will rewrite them
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// into a constant.
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if (!MO.isReg() || MO.isImplicit() || MO.isUndef())
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continue;
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Register Reg = MO.getReg();

‎llvm/lib/CodeGen/StackMaps.cpp

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@@ -268,12 +268,6 @@ StackMaps::parseOperand(MachineInstr::const_mop_iterator MOI,
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if (MOI->isImplicit())
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return ++MOI;
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if (MOI->isUndef()) {
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// Record `undef` register as constant. Use same value as ISel uses.
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Locs.emplace_back(Location::Constant, sizeof(int64_t), 0, 0xFEFEFEFE);
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return ++MOI;
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}
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assert(MOI->getReg().isPhysical() &&
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"Virtreg operands should have been rewritten before now.");
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const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(MOI->getReg());

‎llvm/test/CodeGen/X86/stackmap-undef-operand-anyregcc.mir

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,77 @@
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# RUN: llc -mtriple=x86_64-apple-darwin -start-after=virtregrewriter -o - %s | FileCheck %s
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# Check there's no assertion for anyregcc with an undef operand to a stackmap.
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# CHECK: __LLVM_StackMaps:
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# CHECK-NEXT: .byte 3
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .short 0
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# CHECK-NEXT: .long 1
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# CHECK-NEXT: .long 0
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# CHECK-NEXT: .long 1
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# CHECK-NEXT: .quad _undef_anyregcc_patchpoint
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# CHECK-NEXT: .quad 8
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# CHECK-NEXT: .quad 1
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# CHECK-NEXT: .quad 12
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# CHECK-NEXT: .long Ltmp0-_undef_anyregcc_patchpoint
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# CHECK-NEXT: .short 0
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# CHECK-NEXT: .short 2
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# CHECK-NEXT: .byte 1
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .short 8
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# CHECK-NEXT: .short 0
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# CHECK-NEXT: .short 0
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# CHECK-NEXT: .long 0
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# CHECK-NEXT: .byte 1
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .short 8
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# CHECK-NEXT: .short 0
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# CHECK-NEXT: .short 0
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# CHECK-NEXT: .long 0
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# CHECK-NEXT: .p2align 3, 0x0
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# CHECK-NEXT: .short 0
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# CHECK-NEXT: .short 7
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# CHECK-NEXT: .short 0
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .byte 8
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# CHECK-NEXT: .short 3
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .byte 8
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# CHECK-NEXT: .short 7
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .byte 8
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# CHECK-NEXT: .short 12
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .byte 8
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# CHECK-NEXT: .short 13
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .byte 8
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# CHECK-NEXT: .short 14
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .byte 8
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# CHECK-NEXT: .short 15
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# CHECK-NEXT: .byte 0
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# CHECK-NEXT: .byte 8
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# CHECK-NEXT: .p2align 3
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---
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name: undef_anyregcc_patchpoint
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tracksRegLiveness: true
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frameInfo:
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hasPatchPoint: true
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hasCalls: true
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adjustsStack: true
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fixedStack:
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- { id: 0, type: default, offset: 72, size: 8, alignment: 8, stack-id: default,
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isImmutable: true, isAliased: false, callee-saved-register: '', callee-saved-restored: true,
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debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
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body: |
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bb.0:
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liveins: $rcx, $rdi, $rdx, $rsi, $r8, $r9
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ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
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dead renamable $rax = MOV64rm %fixed-stack.0, 1, $noreg, 0, $noreg :: (load (s64) from %fixed-stack.0)
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renamable $rax = PATCHPOINT 12, 15, 0, 1, 13, undef renamable $rax, csr_64_allregs, implicit-def dead early-clobber $r11, implicit-def $rsp, implicit-def $ssp
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ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
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RET 0, $rax
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...

‎llvm/test/CodeGen/X86/statepoint-fixup-undef.mir

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -181,13 +181,13 @@ body: |
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; STACKMAP-NEXT: .short 3
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; STACKMAP-NEXT: .short 0
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; STACKMAP-NEXT: .long 0
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; This is a constant 0xFEFEFEFE we are looking for
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; STACKMAP-NEXT: .byte 4
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; This is entry we're looking for
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; STACKMAP-NEXT: .byte 1
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; STACKMAP-NEXT: .byte 0
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; STACKMAP-NEXT: .short 8
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; STACKMAP-NEXT: .short 4
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; STACKMAP-NEXT: .short 0
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; STACKMAP-NEXT: .short 0
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; STACKMAP-NEXT: .long -16843010
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; STACKMAP-NEXT: .long 0
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; STACKMAP-NEXT: .byte 4
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; STACKMAP-NEXT: .byte 0
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; STACKMAP-NEXT: .short 8

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