[CodeGenPrepare] Zap the argument of llvm.assume when deleting it

We know that the argument is mostly likely dead, so we can purge it
early. Otherwise it would make it to codegen, and can block further
optimizations.

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 2034fd0..3272f36 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -2044,7 +2044,12 @@ bool CodeGenPrepare::optimizeCallInst(CallInst *CI, bool &ModifiedDT) {
     switch (II->getIntrinsicID()) {
     default: break;
     case Intrinsic::assume: {
+      Value *Operand = II->getOperand(0);
       II->eraseFromParent();
+      // Prune the operand, it's most likely dead.
+      RecursivelyDeleteTriviallyDeadInstructions(
+          Operand, TLInfo, nullptr,
+          [&](Value *V) { removeAllAssertingVHReferences(V); });
       return true;
     }