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[SEH] Fix register liveness verification for EHa #76933

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[SEH] Fix register liveness verification for EHa #76933

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8305e5e
[SEH] Add test to track EHa register liveness verification
HaohaiWen Jan 4, 2024
2d60e94
Fix typo
HaohaiWen Jan 4, 2024
26291fe
Remove attributes
HaohaiWen Jan 4, 2024
74f5abb
[SEH] Fix register liveness verification for EHa
HaohaiWen Jan 4, 2024
9fc5b2c
Merge remote-tracking branch 'origin/main' into eha-bug-fix
HaohaiWen Jan 4, 2024
d6786e4
Only do not check seh handler
HaohaiWen Jan 5, 2024
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35 changes: 32 additions & 3 deletions llvm/lib/CodeGen/MachineVerifier.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBundle.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
Expand Down Expand Up @@ -3347,10 +3348,37 @@ void MachineVerifier::verifyLiveRangeSegment(const LiveRange &LR,
OwnerLI.computeSubRangeUndefs(Undefs, LaneMask, *MRI, *Indexes);
}

bool IsEHa = MF->getMMI().getModule()->getModuleFlag("eh-asynch");
while (true) {
assert(LiveInts->isLiveInToMBB(LR, &*MFI));
// We don't know how to track physregs into a landing pad.
if (!Reg.isVirtual() && MFI->isEHPad()) {
auto IsSEHHandler = [](const MachineBasicBlock &Handler) -> bool {
if (!Handler.isMachineBlockAddressTaken())
return false;

for (const User *U : Handler.getBasicBlock()->users()) {
if (!isa<InvokeInst>(U))
continue;
const Function *Fn = cast<CallBase>(U)->getCalledFunction();
if (!Fn || !Fn->isIntrinsic())
continue;

switch (Fn->getIntrinsicID()) {
default:
continue;
case Intrinsic::seh_scope_begin:
case Intrinsic::seh_scope_end:
case Intrinsic::seh_try_begin:
case Intrinsic::seh_try_end:
return true;
}
}
return false;
};

// TODO: we don't know how to track physregs into a landing pad. For async
// EH, the virtual reg lives before scope begin, but we don't know seh scope
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Can we get the scope through seh_scope_begin/seh_scope_end etc.?

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@HaohaiWen HaohaiWen Jan 5, 2024 •
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seh_scope_begin/seh_scope_end is lowered to fall through jmp which can be eliminated.
e.g.

BB0:
  instA
  jmp BB1:
BB1:
  invoke llvm.seh.scope.begin to BB2
BB2:
  instB

Those BB0, BB1, BB2 can be optimized to

MBB0:
   EH_LABEL
   instA
   EH_LABEL
   EH_LABEL
   instB
   EH_LABEL

We don't know which MBB the BB2 is mapped to. We also don't know which EH_LABEL the llvm.seh.scope.begin locate.

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I once had an idea to lower them into pseudo instructions. But maybe need more work to do.

// range of landing pad in Machine IR. Therefore don't check its liveness.
if (MFI->isEHPad() && (!Reg.isVirtual() || (IsEHa && IsSEHHandler(*MFI)))) {
if (&*MFI == EndMBB)
break;
++MFI;
Expand All @@ -3364,8 +3392,9 @@ void MachineVerifier::verifyLiveRangeSegment(const LiveRange &LR,
// Check that VNI is live-out of all predecessors.
for (const MachineBasicBlock *Pred : MFI->predecessors()) {
SlotIndex PEnd = LiveInts->getMBBEndIdx(Pred);
// Predecessor of landing pad live-out on last call.
// Predecessor of landing pad live-out on last call for sync EH.
if (MFI->isEHPad()) {
assert(!IsEHa && "EHa may raise exception on non call");
for (const MachineInstr &MI : llvm::reverse(*Pred)) {
if (MI.isCall()) {
PEnd = Indexes->getInstructionIndex(MI).getBoundaryIndex();
Expand Down
1 change: 0 additions & 1 deletion llvm/test/CodeGen/X86/windows-seh-EHa-RegisterLiveness.ll
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@@ -1,4 +1,3 @@
; XFAIL: *
; RUN: llc --verify-machineinstrs < %s
source_filename = "test.cpp"
target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
Expand Down