[llvm] [SEH] Fix register liveness verification for EHa (PR #76933)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: None (HaohaiWen)

<details>
<summary>Changes</summary>

For sync EH, exception can only happen on last call of machine basic
block. For async EH, exception can happen on any place within seh scope.
For register lives into landing pad, it should live before entering seh
scope. However, we don't know the scope range in machine IR. Therefore
don't check its liveness under EHa.

---
Full diff: https://github.com/llvm/llvm-project/pull/76933.diff


2 Files Affected:

- (modified) llvm/lib/CodeGen/MachineVerifier.cpp (+8-3) 
- (added) llvm/test/CodeGen/X86/windows-seh-EHa-RegisterLiveness.ll (+65) 


``````````diff
diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index a015d9bbd2d3f5..08f5ddfccc4f60 100644
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -48,6 +48,7 @@
 #include "llvm/CodeGen/MachineMemOperand.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/PseudoSourceValue.h"
 #include "llvm/CodeGen/RegisterBank.h"
 #include "llvm/CodeGen/RegisterBankInfo.h"
@@ -3347,10 +3348,13 @@ 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()) {
+    // 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
+    // range of landing pad in Machine IR. Therefore don't check its liveness.
+    if (MFI->isEHPad() && (!Reg.isVirtual() || IsEHa)) {
       if (&*MFI == EndMBB)
         break;
       ++MFI;
@@ -3364,8 +3368,9 @@ 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();
diff --git a/llvm/test/CodeGen/X86/windows-seh-EHa-RegisterLiveness.ll b/llvm/test/CodeGen/X86/windows-seh-EHa-RegisterLiveness.ll
new file mode 100644
index 00000000000000..20f91702c08849
--- /dev/null
+++ b/llvm/test/CodeGen/X86/windows-seh-EHa-RegisterLiveness.ll
@@ -0,0 +1,65 @@
+; 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"
+target triple = "x86_64-pc-windows-msvc19.12.0"
+
+$"?test at Test@@Plugin@@Host@@@Z" = comdat any
+
+declare i32 @__CxxFrameHandler3(...)
+
+; Function Attrs: nounwind memory(none)
+declare void @llvm.seh.scope.begin() #1
+
+; Function Attrs: nobuiltin allocsize(0)
+declare ptr @"??2 at Test@Z"(i64) #1
+
+; Function Attrs: nounwind memory(none)
+declare void @llvm.seh.scope.end() #0
+
+; Function Attrs: nobuiltin nounwind
+declare void @"??3 at YAXPEAX@Z"(ptr) #2
+
+; Function Attrs: mustprogress uwtable
+define ptr @"?test at Test@@Plugin@@Host@@@Z"(ptr %this, ptr %host) #3 comdat align 2 personality ptr @__CxxFrameHandler3 {
+entry:
+  %host.addr = alloca ptr, align 8
+  %this.addr = alloca ptr, align 8
+  store ptr %host, ptr %host.addr, align 8
+  store ptr %this, ptr %this.addr, align 8
+  %this1 = load ptr, ptr %this.addr, align 8
+  %call = call noalias ptr @"??2 at Test@Z"(i64 152) #5
+  invoke void @llvm.seh.scope.begin()
+          to label %invoke.cont unwind label %ehcleanup
+
+invoke.cont:                                      ; preds = %entry
+  %call3 = invoke ptr @"??Test@?A0x2749C4FD@@QEAA at Test@Test@@@Z"(ptr %call, ptr %this1)
+          to label %invoke.cont2 unwind label %ehcleanup
+
+invoke.cont2:                                     ; preds = %invoke.cont
+  invoke void @llvm.seh.scope.end()
+          to label %invoke.cont4 unwind label %ehcleanup
+
+invoke.cont4:                                     ; preds = %invoke.cont2
+  ret ptr %call
+
+ehcleanup:                                        ; preds = %invoke.cont2, %invoke.cont, %entry
+  %0 = cleanuppad within none []
+  call void @"??3 at YAXPEAX@Z"(ptr %call) #6 [ "funclet"(token %0) ]
+  cleanupret from %0 unwind to caller
+}
+
+; Function Attrs: uwtable
+declare hidden ptr @"??Test@?A0x2749C4FD@@QEAA at Test@Test@@@Z"(ptr, ptr) #4 align 2
+
+attributes #0 = { nounwind memory(none) }
+attributes #1 = { nobuiltin allocsize(0) "target-cpu"="x86-64" "target-features"="+cmov,+crc32,+cx8,+fxsr,+mmx,+popcnt,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+ssse3,+x87" "tune-cpu"="generic" }
+attributes #2 = { nobuiltin nounwind "target-cpu"="x86-64" "target-features"="+cmov,+crc32,+cx8,+fxsr,+mmx,+popcnt,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+ssse3,+x87" "tune-cpu"="generic" }
+attributes #3 = { mustprogress uwtable "target-cpu"="x86-64" "target-features"="+cmov,+crc32,+cx8,+fxsr,+mmx,+popcnt,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+ssse3,+x87" "tune-cpu"="generic" }
+attributes #4 = { uwtable "target-cpu"="x86-64" "target-features"="+cmov,+crc32,+cx8,+fxsr,+mmx,+popcnt,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+ssse3,+x87" "tune-cpu"="generic" }
+attributes #5 = { builtin allocsize(0) }
+attributes #6 = { builtin nounwind }
+
+!llvm.module.flags = !{!1, !2}
+
+!1 = !{i32 2, !"eh-asynch", i32 1}
+!2 = !{i32 7, !"uwtable", i32 2}

``````````

</details>


https://github.com/llvm/llvm-project/pull/76933