[BranchFolding][WinEH] Do not remove EH pads#176735
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If branch folding remoes an EH pad, we're left with a dangling reference to it from the CxxUnwindMap. We could try to fix this up, but given that this should be a rare situation, just leave the dead EH pad blocks around.
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@llvm/pr-subscribers-backend-aarch64 Author: Nikita Popov (nikic) ChangesIf branch folding remoes an EH pad, we're left with a dangling reference to it from the CxxUnwindMap. We could try to fix this up, but given that this should be a rare situation, just leave the dead EH pad blocks around. Fixes #176421. 2 Files Affected:
diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 9a12039291989..5a43f4e1ec993 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -1259,7 +1259,8 @@ bool BranchFolder::OptimizeBranches(MachineFunction &MF) {
MadeChange |= OptimizeBlock(&MBB);
// If it is dead, remove it.
- if (MBB.pred_empty() && !MBB.isMachineBlockAddressTaken()) {
+ if (MBB.pred_empty() && !MBB.isMachineBlockAddressTaken() &&
+ !MBB.isEHPad()) {
RemoveDeadBlock(&MBB);
MadeChange = true;
++NumDeadBlocks;
diff --git a/llvm/test/CodeGen/AArch64/wineh-dangling-eh-pad-reference.ll b/llvm/test/CodeGen/AArch64/wineh-dangling-eh-pad-reference.ll
new file mode 100644
index 0000000000000..e20d4ce3633d7
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/wineh-dangling-eh-pad-reference.ll
@@ -0,0 +1,34 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
+; RUN: llc -mtriple=aarch64-pc-windows-msvc < %s | FileCheck %s
+
+declare void @func()
+
+; Make sure that we do not end up with a dangling EH pad reference.
+
+define void @test(ptr %p) personality ptr @__CxxFrameHandler3 {
+; CHECK-LABEL: test:
+; CHECK: .seh_proc "?dtor$1@?0?test@4HA"
+; CHECK-LABEL: $stateUnwindMap$test:
+; CHECK: .word -1 // ToState
+; CHECK: .word "?dtor$1@?0?test@4HA"@IMGREL // Action
+
+ %v0 = load i32, ptr %p
+ %v1 = load i32, ptr %p
+ %xor = xor i32 %v0, %v1
+ %cmp = icmp eq i32 %xor, 0
+ br i1 %cmp, label %exit, label %bb
+
+bb:
+ invoke void @func()
+ to label %exit unwind label %unwind
+
+unwind:
+ %cp = cleanuppad within none []
+ store volatile i32 0, ptr %p
+ cleanupret from %cp unwind to caller
+
+exit:
+ ret void
+}
+
+declare i32 @__CxxFrameHandler3(...)
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rnk
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Jan 20, 2026
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Jan 26, 2026
If branch folding remoes an EH pad, we're left with a dangling reference to it from the CxxUnwindMap. We could try to fix this up, but given that this should be a rare situation, just leave the dead EH pad blocks around. Fixes llvm#176421. (cherry picked from commit 528bb2b)
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If branch folding remoes an EH pad, we're left with a dangling reference to it from the CxxUnwindMap. We could try to fix this up, but given that this should be a rare situation, just leave the dead EH pad blocks around.
Fixes #176421.