[PATCH] D138072: [llvm-reduce] Do not crash when accessing landingpads of invokes.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: arsenm, aeubanks.
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During basic-block reductions, landing pads can get removed. If there
are multiple invokes that share the same landing pad,
Invoke->getLandingPadInst() for the second invoke will crash because
IR is now temporarily invalid, breaking the assumption that a landing
pad instruction must exist.

To avoid crashing just look for the landing pad manually and account for
the possibility that it may not exist.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D138072

Files:
  llvm/test/tools/llvm-reduce/invoke-with-missing-landingpad.ll
  llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp


Index: llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
===================================================================
--- llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
+++ llvm/tools/llvm-reduce/deltas/ReduceBasicBlocks.cpp
@@ -47,9 +47,11 @@
 
   bool IsBranch = isa<BranchInst>(Term);
   if (InvokeInst *Invoke = dyn_cast<InvokeInst>(Term)) {
-    LandingPadInst *LP = Invoke->getLandingPadInst();
-    LP->replaceAllUsesWith(getDefaultValue(LP->getType()));
-    LP->eraseFromParent();
+    if (LandingPadInst *LP = dyn_cast_or_null<LandingPadInst>(
+            Invoke->getUnwindDest()->getFirstNonPHI())) {
+      LP->replaceAllUsesWith(getDefaultValue(LP->getType()));
+      LP->eraseFromParent();
+    }
     IsBranch = true;
   }
 
Index: llvm/test/tools/llvm-reduce/invoke-with-missing-landingpad.ll
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-reduce/invoke-with-missing-landingpad.ll
@@ -0,0 +1,37 @@
+; RUN: llvm-reduce --delta-passes=basic-blocks --test FileCheck --test-arg --check-prefixes=CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck <%t %s
+
+; CHECK-INTERESTINGNESS: call void @foo()
+
+; CHECK: define void @test() personality ptr null {
+; CHECK-NEXT: entry:
+; CHECK-NEXT:   br label %cont
+; CHECK-EMPTY:
+; CHECK-NEXT: cont:
+; CHECK-NEXT:   br label %exit
+; CHECK-EMPTY:
+; CHECK-NEXT: exit:
+; CHECK-NEXT:   call void @foo()
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }
+
+define void @test() personality ptr null {
+entry:
+  invoke void @foo()
+          to label %cont unwind label %lpad
+
+cont:
+  invoke void @foo()
+          to label %exit unwind label %lpad
+
+lpad:
+  %0 = landingpad { ptr, i32 }
+          cleanup
+  ret void
+
+exit:
+  call void @foo()
+  ret void
+}
+
+declare void @foo()


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