[CodeGenPrepare] Fix zapping dead operands of assume

This patch fixes a problem of the commit 52cc97a0.
A test case is created to demonstrate the crash caused by
the instruction iterator invalidated by the recursive
removal of dead operands of assume. The solution restarts
from the blocks's first instruction in case CurInstIterator
is invalidated by RecursivelyDeleteTriviallyDeadInstructions().

Reviewed By: bkramer

Differential Revision: https://reviews.llvm.org/D87434

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 529975c..bb0bad7 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -2047,9 +2047,11 @@ bool CodeGenPrepare::optimizeCallInst(CallInst *CI, bool &ModifiedDT) {
       Value *Operand = II->getOperand(0);
       II->eraseFromParent();
       // Prune the operand, it's most likely dead.
-      RecursivelyDeleteTriviallyDeadInstructions(
-          Operand, TLInfo, nullptr,
-          [&](Value *V) { removeAllAssertingVHReferences(V); });
+      resetIteratorIfInvalidatedWhileCalling(BB, [&]() {
+        RecursivelyDeleteTriviallyDeadInstructions(
+            Operand, TLInfo, nullptr,
+            [&](Value *V) { removeAllAssertingVHReferences(V); });
+      });
       return true;
     }