[llvm] 2e0ded3 - [Windows SEH] Fix crash on empty seh block (#107031)

[via llvm-commits]

Author: R-Goc
Date: 2024-09-04T22:10:36+04:00
New Revision: 2e0ded3371f8d42f376bdfd4d70687537e36818e

URL: https://github.com/llvm/llvm-project/commit/2e0ded3371f8d42f376bdfd4d70687537e36818e
DIFF: https://github.com/llvm/llvm-project/commit/2e0ded3371f8d42f376bdfd4d70687537e36818e.diff

LOG: [Windows SEH] Fix crash on empty seh block (#107031)

Fixes https://github.com/llvm/llvm-project/issues/105813 and
https://github.com/llvm/llvm-project/issues/106915.
Adds a check for the end of the iterator, which can be a sentinel. 
The issue was introduced in
https://github.com/llvm/llvm-project/commit/0efe111365ae176671e01252d24028047d807a84
from what I can see, so along with the introduction of /EHa support.

Added: 
    llvm/test/CodeGen/WinEH/wineh-empty-seh-scope.ll

Modified: 
    llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index b37e54d66ddf51..263a213bd4f641 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -1476,6 +1476,10 @@ void SelectionDAGISel::reportIPToStateForBlocks(MachineFunction *MF) {
     if (BB->getFirstMayFaultInst()) {
       // Report IP range only for blocks with Faulty inst
       auto MBBb = MBB.getFirstNonPHI();
+
+      if (MBBb == MBB.end())
+        continue;
+
       MachineInstr *MIb = &*MBBb;
       if (MIb->isTerminator())
         continue;

diff  --git a/llvm/test/CodeGen/WinEH/wineh-empty-seh-scope.ll b/llvm/test/CodeGen/WinEH/wineh-empty-seh-scope.ll
new file mode 100644
index 00000000000000..5f382f10f180bc
--- /dev/null
+++ b/llvm/test/CodeGen/WinEH/wineh-empty-seh-scope.ll
@@ -0,0 +1,18 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=x86_64-pc-windows-msvc19.41.34120 < %s | FileCheck %s
+
+define void @foo() personality ptr @__CxxFrameHandler3 {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    nop # avoids zero-length function
+  call void @llvm.seh.scope.begin()
+  unreachable
+}
+
+declare i32 @__CxxFrameHandler3(...)
+
+declare void @llvm.seh.scope.begin()
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 2, !"eh-asynch", i32 1}