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[CFIFixup] Add frame info to the first block of each section #113626

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merged 1 commit into from
Nov 20, 2024
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[CFIFixup] Add frame info to the first block of each section #113626

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69 changes: 58 additions & 11 deletions llvm/lib/CodeGen/CFIFixup.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,12 @@

#include "llvm/CodeGen/CFIFixup.h"

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
Expand All @@ -76,6 +81,8 @@
#include "llvm/MC/MCDwarf.h"
#include "llvm/Target/TargetMachine.h"

#include <iterator>

using namespace llvm;

#define DEBUG_TYPE "cfi-fixup"
Expand Down Expand Up @@ -120,7 +127,7 @@ findPrologueEnd(MachineFunction &MF, MachineBasicBlock::iterator &PrologueEnd) {
// iterator can point to the end of the block. Instructions are inserted
// *before* the iterator.
struct InsertionPoint {
MachineBasicBlock *MBB;
MachineBasicBlock *MBB = nullptr;
MachineBasicBlock::iterator Iterator;
};

Expand Down Expand Up @@ -150,6 +157,30 @@ insertRememberRestorePair(const InsertionPoint &RememberInsertPt,
->getIterator())};
}

// Copies all CFI instructions before PrologueEnd and inserts them before
// DstInsertPt. Returns the iterator to the first instruction after the
// inserted instructions.
static InsertionPoint cloneCfiPrologue(const InsertionPoint &PrologueEnd,
const InsertionPoint &DstInsertPt) {
MachineFunction &MF = *DstInsertPt.MBB->getParent();

auto cloneCfiInstructions = [&](MachineBasicBlock::iterator Begin,
MachineBasicBlock::iterator End) {
auto ToClone = map_range(
make_filter_range(make_range(Begin, End), isPrologueCFIInstruction),
[&](const MachineInstr &MI) { return MF.CloneMachineInstr(&MI); });
DstInsertPt.MBB->insert(DstInsertPt.Iterator, ToClone.begin(),
ToClone.end());
};

// Clone all CFI instructions from previous blocks.
for (auto &MBB : make_range(MF.begin(), PrologueEnd.MBB->getIterator()))
cloneCfiInstructions(MBB.begin(), MBB.end());
// Clone all CFI instructions from the final prologue block.
cloneCfiInstructions(PrologueEnd.MBB->begin(), PrologueEnd.Iterator);
return DstInsertPt;
}

bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
const TargetFrameLowering &TFL = *MF.getSubtarget().getFrameLowering();
if (!TFL.enableCFIFixup(MF))
Expand All @@ -172,7 +203,8 @@ bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
bool HasFrameOnEntry : 1;
bool HasFrameOnExit : 1;
};
SmallVector<BlockFlags, 32> BlockInfo(NumBlocks, {false, false, false, false});
SmallVector<BlockFlags, 32> BlockInfo(NumBlocks,
{false, false, false, false});
BlockInfo[0].Reachable = true;
BlockInfo[0].StrongNoFrameOnEntry = true;

Expand Down Expand Up @@ -209,10 +241,11 @@ bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
// of the previous block. If the intended frame state is different, insert
// compensating CFI instructions.
bool Change = false;
// `InsertPt` always points to the point in a preceding block where we have to
// insert a `.cfi_remember_state`, in the case that the current block needs a
// `.cfi_restore_state`.
InsertionPoint InsertPt = {PrologueBlock, PrologueEnd};
// `InsertPt[sectionID]` always points to the point in a preceding block where
// we have to insert a `.cfi_remember_state`, in the case that the current
// block needs a `.cfi_restore_state`.
SmallDenseMap<MBBSectionID, InsertionPoint> InsertionPts;
InsertionPts[PrologueBlock->getSectionID()] = {PrologueBlock, PrologueEnd};

assert(PrologueEnd != PrologueBlock->begin() &&
"Inconsistent notion of \"prologue block\"");
Expand All @@ -239,14 +272,28 @@ bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
}
}
#endif

// If the block is the first block in its section, then it doesn't have a
// frame on entry.
HasFrame &= !CurrBB->isBeginSection();
if (!Info.StrongNoFrameOnEntry && Info.HasFrameOnEntry && !HasFrame) {
// Reset to the "after prologue" state.

// There's an earlier block known to have a stack frame. Insert a
// `.cfi_remember_state` instruction into that block and a
// `.cfi_restore_state` instruction at the beginning of the current block.
InsertPt = insertRememberRestorePair(
InsertPt, InsertionPoint{&*CurrBB, CurrBB->begin()});
InsertionPoint &InsertPt = InsertionPts[CurrBB->getSectionID()];
if (InsertPt.MBB == nullptr) {
// CurBB is the first block in its section, so there is no "after
// prologue" state. Clone the CFI instructions from the prologue block
// to create it.
InsertPt = cloneCfiPrologue({PrologueBlock, PrologueEnd},
{&*CurrBB, CurrBB->begin()});
} else {
// There's an earlier block known to have a stack frame. Insert a
// `.cfi_remember_state` instruction into that block and a
// `.cfi_restore_state` instruction at the beginning of the current
// block.
InsertPt =
insertRememberRestorePair(InsertPt, {&*CurrBB, CurrBB->begin()});
}
Change = true;
} else if ((Info.StrongNoFrameOnEntry || !Info.HasFrameOnEntry) &&
HasFrame) {
Expand Down
200 changes: 200 additions & 0 deletions llvm/test/CodeGen/AArch64/cfi-fixup-multi-section.mir
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Original file line number Diff line number Diff line change
@@ -0,0 +1,200 @@
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
# RUN: llc -mtriple=aarch64 -run-pass=cfi-fixup %s -o - | FileCheck %s
--- |
define i32 @f0(i32 %x) #0 {
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" }

...
---
name: f0
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: []
machineFunctionInfo:
hasRedZone: false
body: |
; CHECK-LABEL: name: f0
; 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: CFI_INSTRUCTION remember_state
; 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: CFI_INSTRUCTION restore_state
; CHECK-NEXT: CFI_INSTRUCTION remember_state
; 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: CFI_INSTRUCTION restore_state
; 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


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