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[CFIFixup] Fixup CFI for split functions with synchronous uwtables #125299

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Feb 11, 2025
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[CFIFixup] Fixup CFI for split functions with synchronous uwtables #125299

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2e9b586
Precommit tests for synchronous uwtable CFI fixup
dhoekwater Jan 31, 2025
b29f23b
[CFIFixup] Fixup CFI for split functions with synchronous uwtables
dhoekwater Jan 31, 2025
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11 changes: 9 additions & 2 deletions llvm/include/llvm/CodeGen/TargetFrameLowering.h
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Original file line number Diff line number Diff line change
Expand Up @@ -229,10 +229,17 @@ class TargetFrameLowering {

/// Returns true if we may need to fix the unwind information for the
/// function.
virtual bool enableCFIFixup(MachineFunction &MF) const;
virtual bool enableCFIFixup(const MachineFunction &MF) const;

/// enableFullCFIFixup - Returns true if we may need to fix the unwind
/// information such that it is accurate for *every* instruction in the
/// function (e.g. if the function has an async unwind table).
virtual bool enableFullCFIFixup(const MachineFunction &MF) const {
return enableCFIFixup(MF);
};

/// Emit CFI instructions that recreate the state of the unwind information
/// upon fucntion entry.
/// upon function entry.
virtual void resetCFIToInitialState(MachineBasicBlock &MBB) const {}

/// Replace a StackProbe stub (if any) with the actual probe code inline
Expand Down
6 changes: 6 additions & 0 deletions llvm/lib/CodeGen/CFIFixup.cpp
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Expand Up @@ -80,6 +80,7 @@
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Target/TargetMachine.h"

#include <iterator>
Expand Down Expand Up @@ -252,6 +253,11 @@ fixupBlock(MachineBasicBlock &CurrBB, const BlockFlagsVector &BlockInfo,
if (!Info.Reachable)
return false;

// If we don't need to perform full CFI fix up, we only need to fix up the
// first basic block in the section.
if (!TFL.enableFullCFIFixup(MF) && !CurrBB.isBeginSection())
return false;

// If the previous block and the current block are in the same section,
// the frame info will propagate from the previous block to the current one.
const BlockFlags &PrevInfo =
Expand Down
2 changes: 1 addition & 1 deletion llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp
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Expand Up @@ -35,7 +35,7 @@ bool TargetFrameLowering::enableCalleeSaveSkip(const MachineFunction &MF) const
return false;
}

bool TargetFrameLowering::enableCFIFixup(MachineFunction &MF) const {
bool TargetFrameLowering::enableCFIFixup(const MachineFunction &MF) const {
return MF.needsFrameMoves() &&
!MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
}
Expand Down
7 changes: 6 additions & 1 deletion llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
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Expand Up @@ -2612,8 +2612,13 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
}
}

bool AArch64FrameLowering::enableCFIFixup(MachineFunction &MF) const {
bool AArch64FrameLowering::enableCFIFixup(const MachineFunction &MF) const {
return TargetFrameLowering::enableCFIFixup(MF) &&
MF.getInfo<AArch64FunctionInfo>()->needsDwarfUnwindInfo(MF);
}

bool AArch64FrameLowering::enableFullCFIFixup(const MachineFunction &MF) const {
return enableCFIFixup(MF) &&
MF.getInfo<AArch64FunctionInfo>()->needsAsyncDwarfUnwindInfo(MF);
}

Expand Down
4 changes: 3 additions & 1 deletion llvm/lib/Target/AArch64/AArch64FrameLowering.h
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Expand Up @@ -36,7 +36,9 @@ class AArch64FrameLowering : public TargetFrameLowering {
void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;

bool enableCFIFixup(MachineFunction &MF) const override;
bool enableCFIFixup(const MachineFunction &MF) const override;

bool enableFullCFIFixup(const MachineFunction &MF) const override;

bool canUseAsPrologue(const MachineBasicBlock &MBB) const override;

Expand Down
187 changes: 187 additions & 0 deletions llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir
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Expand Up @@ -10,9 +10,19 @@
ret i32 0
}

define i32 @f1(i32 %x) #1 {
entry: br label %return
if.end: br label %return
if.then2: br label %return
if.else: br label %return
return:
ret i32 0
}

declare i32 @g(i32)

attributes #0 = { nounwind shadowcallstack uwtable "sign-return-address"="non-leaf" "target-features"="+reserve-x18" }
attributes #1 = { nounwind shadowcallstack uwtable(sync) "sign-return-address"="non-leaf" "target-features"="+reserve-x18" }

...
---
Expand Down Expand Up @@ -197,4 +207,181 @@ body: |
B %bb.7


...
---
name: f1
alignment: 4
exposesReturnsTwice: false
legalized: false
regBankSelected: false
selected: false
failedISel: false
tracksRegLiveness: true
hasWinCFI: false
failsVerification: false
registers: []
liveins:
- { reg: '$w0', virtual-reg: '' }
frameInfo:
isFrameAddressTaken: false
isReturnAddressTaken: false
hasStackMap: false
hasPatchPoint: false
stackSize: 16
offsetAdjustment: 0
maxAlignment: 16
adjustsStack: true
hasCalls: true
stackProtector: ''
maxCallFrameSize: 0
cvBytesOfCalleeSavedRegisters: 0
hasOpaqueSPAdjustment: false
hasVAStart: false
hasMustTailInVarArgFunc: false
hasTailCall: false
localFrameSize: 0
savePoint: ''
restorePoint: ''
fixedStack: []
stack:
- { id: 0, name: '', type: spill-slot, offset: -16, size: 8, alignment: 16,
stack-id: default, callee-saved-register: '$lr', callee-saved-restored: true,
debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
callSites: []
debugValueSubstitutions: []
constants: []
body: |
; CHECK-LABEL: name: f1
; CHECK: bb.0.entry:
; CHECK-NEXT: successors: %bb.4(0x30000000), %bb.1(0x50000000)
; CHECK-NEXT: liveins: $w0, $lr, $x18
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: CBZW renamable $w0, %bb.4
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.1.if.end:
; CHECK-NEXT: successors: %bb.3(0x30000000), %bb.2(0x50000000)
; CHECK-NEXT: liveins: $w0, $lr, $x18
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: early-clobber $x18 = frame-setup STRXpost $lr, $x18, 8
; CHECK-NEXT: frame-setup CFI_INSTRUCTION escape 0x16, 0x12, 0x02, 0x82, 0x78
; CHECK-NEXT: frame-setup PACIASP implicit-def $lr, implicit killed $lr, implicit $sp
; CHECK-NEXT: frame-setup CFI_INSTRUCTION negate_ra_sign_state
; CHECK-NEXT: early-clobber $sp = frame-setup STRXpre killed $lr, $sp, -16 :: (store (s64) into %stack.0)
; CHECK-NEXT: frame-setup CFI_INSTRUCTION def_cfa_offset 16
; CHECK-NEXT: frame-setup CFI_INSTRUCTION offset $w30, -16
; CHECK-NEXT: TBNZW renamable $w0, 31, %bb.3
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.2.if.else:
; CHECK-NEXT: successors: %bb.5(0x80000000)
; CHECK-NEXT: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: renamable $w0 = nuw nsw ADDWri killed renamable $w0, 1, 0
; CHECK-NEXT: BL @g, csr_aarch64_aapcs_scs, implicit-def dead $lr, implicit $sp, implicit killed $w0, implicit-def $sp, implicit-def $w0
; CHECK-NEXT: renamable $w8 = MOVZWi 1, 0
; CHECK-NEXT: $w0 = SUBWrs killed renamable $w8, killed renamable $w0, 0
; CHECK-NEXT: B %bb.5
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.3.if.then2 (bbsections 1):
; CHECK-NEXT: successors: %bb.5(0x80000000)
; CHECK-NEXT: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: frame-setup CFI_INSTRUCTION escape 0x16, 0x12, 0x02, 0x82, 0x78
; CHECK-NEXT: frame-setup CFI_INSTRUCTION negate_ra_sign_state
; CHECK-NEXT: frame-setup CFI_INSTRUCTION def_cfa_offset 16
; CHECK-NEXT: frame-setup CFI_INSTRUCTION offset $w30, -16
; CHECK-NEXT: renamable $w0 = nsw SUBWri killed renamable $w0, 1, 0
; CHECK-NEXT: BL @g, csr_aarch64_aapcs_scs, implicit-def dead $lr, implicit $sp, implicit killed $w0, implicit-def $sp, implicit-def $w0
; CHECK-NEXT: renamable $w0 = nsw ADDWri killed renamable $w0, 1, 0
; CHECK-NEXT: B %bb.5
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.4.return:
; CHECK-NEXT: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: RET undef $lr, implicit killed $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.5.return:
; CHECK-NEXT: successors: %bb.7(0x80000000)
; CHECK-NEXT: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: B %bb.7
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.6.return:
; CHECK-NEXT: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: early-clobber $sp, $lr = frame-destroy LDRXpost $sp, 16 :: (load (s64) from %stack.0)
; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 0
; CHECK-NEXT: frame-destroy AUTIASP implicit-def $lr, implicit killed $lr, implicit $sp
; CHECK-NEXT: frame-destroy CFI_INSTRUCTION negate_ra_sign_state
; CHECK-NEXT: early-clobber $x18, $lr = frame-destroy LDRXpre $x18, -8
; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w18
; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w30
; CHECK-NEXT: RET undef $lr, implicit killed $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.7.return:
; CHECK-NEXT: successors: %bb.6(0x80000000)
; CHECK-NEXT: liveins: $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: B %bb.6
bb.0.entry:
successors: %bb.4(0x30000000), %bb.1(0x50000000)
liveins: $w0, $lr, $x18

CBZW renamable $w0, %bb.4

bb.1.if.end:
successors: %bb.3(0x30000000), %bb.2(0x50000000)
liveins: $w0, $lr, $x18

early-clobber $x18 = frame-setup STRXpost $lr, $x18, 8
frame-setup CFI_INSTRUCTION escape 0x16, 0x12, 0x02, 0x82, 0x78
frame-setup PACIASP implicit-def $lr, implicit killed $lr, implicit $sp
frame-setup CFI_INSTRUCTION negate_ra_sign_state
early-clobber $sp = frame-setup STRXpre killed $lr, $sp, -16 :: (store (s64) into %stack.0)
frame-setup CFI_INSTRUCTION def_cfa_offset 16
frame-setup CFI_INSTRUCTION offset $w30, -16
TBNZW renamable $w0, 31, %bb.3

bb.2.if.else:
successors: %bb.5(0x80000000)
liveins: $w0

renamable $w0 = nuw nsw ADDWri killed renamable $w0, 1, 0
BL @g, csr_aarch64_aapcs_scs, implicit-def dead $lr, implicit $sp, implicit killed $w0, implicit-def $sp, implicit-def $w0
renamable $w8 = MOVZWi 1, 0
$w0 = SUBWrs killed renamable $w8, killed renamable $w0, 0
B %bb.5

bb.3.if.then2 (bbsections 1):
successors: %bb.5(0x80000000)
liveins: $w0

renamable $w0 = nsw SUBWri killed renamable $w0, 1, 0
BL @g, csr_aarch64_aapcs_scs, implicit-def dead $lr, implicit $sp, implicit killed $w0, implicit-def $sp, implicit-def $w0
renamable $w0 = nsw ADDWri killed renamable $w0, 1, 0
B %bb.5

bb.4.return:
liveins: $w0
RET undef $lr, implicit killed $w0

bb.5.return:
liveins: $w0
B %bb.6

bb.7.return:
liveins: $w0
early-clobber $sp, $lr = frame-destroy LDRXpost $sp, 16 :: (load (s64) from %stack.0)
frame-destroy CFI_INSTRUCTION def_cfa_offset 0
frame-destroy AUTIASP implicit-def $lr, implicit killed $lr, implicit $sp
frame-destroy CFI_INSTRUCTION negate_ra_sign_state
early-clobber $x18, $lr = frame-destroy LDRXpre $x18, -8
frame-destroy CFI_INSTRUCTION restore $w18
frame-destroy CFI_INSTRUCTION restore $w30
RET undef $lr, implicit killed $w0

bb.6.return:
liveins: $w0
B %bb.7


...