[llvm] cfi fixup (PR #125299)
Daniel Hoekwater via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 31 13:42:07 PST 2025
https://github.com/dhoekwater created https://github.com/llvm/llvm-project/pull/125299
- **Precommit tests for synchronous uwtable CFI fixup**
- **[CFIFixup] Fixup CFI for split functions with synchronous uwtables**
>From 6e98d8b9dd6b0d33e52f19920cf4bc8003f50226 Mon Sep 17 00:00:00 2001
From: Daniel Hoekwater <hoekwater at google.com>
Date: Fri, 31 Jan 2025 21:04:55 +0000
Subject: [PATCH 1/2] Precommit tests for synchronous uwtable CFI fixup
---
.../AArch64/cfi-fixup-multi-section.mir | 183 ++++++++++++++++++
1 file changed, 183 insertions(+)
diff --git a/llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir b/llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir
index a24972d1388320..fbced223429e8f 100644
--- a/llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir
+++ b/llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir
@@ -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" }
...
---
@@ -197,4 +207,177 @@ 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: 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
+
+
...
>From eaad7a4e52a0edc51a9271025003cec3b4a4beee Mon Sep 17 00:00:00 2001
From: Daniel Hoekwater <hoekwater at google.com>
Date: Fri, 31 Jan 2025 21:17:08 +0000
Subject: [PATCH 2/2] [CFIFixup] Fixup CFI for split functions with synchronous
uwtables
Commit 6e54fccede402c9ed0e8038aa258a99c5a2773e5 disables CFI fixup for
functions with synchronous tables, breaking CFI for split functions.
Instead, we can disable *block-level* CFI fixup for functions with
synchronous tables.
Unwind tables can be:
- N/A (not present)
- Asynchronous
- Synchronous
Functions without unwind tables don't need CFI fixup (since they don't
care about CFI).
Functions with asynchronous unwind tables must be accurate for each
basic block, so full CFI fixup is necessary.
Functions with synchronous unwind tables only need to be accurate for
each function (specifically, the portion of a function in a given
section). Disabling CFI fixup entirely for functions with synchronous
uwtables may break CFI for a function split between two sections. The
portion in the first section may have valid CFI, while the portion in
the second section is missing a call frame.
Ex:
```
(.text.hot)
Foo (BB1):
<Call frame information>
...
BB2:
...
(.text.split)
BB3:
...
BB4:
<epilogue>
```
Even if `Foo` has a synchronous unwind table, we still need to insert
call frame information into `BB3` so that unwinding the call stack from
`BB3` or `BB4` works properly.
---
llvm/lib/CodeGen/CFIFixup.cpp | 7 +++++++
llvm/lib/Target/AArch64/AArch64FrameLowering.cpp | 2 +-
llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir | 4 ++++
3 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/CodeGen/CFIFixup.cpp b/llvm/lib/CodeGen/CFIFixup.cpp
index 7778aa637ff08d..614cd343e3cb9e 100644
--- a/llvm/lib/CodeGen/CFIFixup.cpp
+++ b/llvm/lib/CodeGen/CFIFixup.cpp
@@ -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>
@@ -243,12 +244,18 @@ fixupBlock(MachineBasicBlock &CurrBB, const BlockFlagsVector &BlockInfo,
SmallDenseMap<MBBSectionID, InsertionPoint> &InsertionPts,
const InsertionPoint &Prologue) {
const MachineFunction &MF = *CurrBB.getParent();
+ const Function &F = MF.getFunction();
const TargetFrameLowering &TFL = *MF.getSubtarget().getFrameLowering();
const BlockFlags &Info = BlockInfo[CurrBB.getNumber()];
if (!Info.Reachable)
return false;
+ // Only async unwind tables need to fix up CFI at the block level. Otherwise,
+ // the function/section level is sufficient.
+ if (F.getUWTableKind() != UWTableKind::Async && !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 =
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index a082a1ebe95bf8..9b1871d26a2e9b 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -2611,7 +2611,7 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
bool AArch64FrameLowering::enableCFIFixup(MachineFunction &MF) const {
return TargetFrameLowering::enableCFIFixup(MF) &&
- MF.getInfo<AArch64FunctionInfo>()->needsAsyncDwarfUnwindInfo(MF);
+ MF.getInfo<AArch64FunctionInfo>()->needsDwarfUnwindInfo(MF);
}
/// getFrameIndexReference - Provide a base+offset reference to an FI slot for
diff --git a/llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir b/llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir
index fbced223429e8f..a4c88be375c014 100644
--- a/llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir
+++ b/llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir
@@ -285,6 +285,10 @@ body: |
; 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
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