[InstCombine] Don't create bitcast when simplifying round-trip

The bitcast was not being added to the worklist. I could switch
this to use the IRBuilder instead, but this bitcast is not relevant
with opaque pointers anyway, so just drop it entirely.

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 5adbb8f..41cbcb1 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -361,7 +361,7 @@ static bool simplifyAssocCastAssoc(BinaryOperator *BinOp1,
   return true;
 }
 
-// Simplifies IntToPtr/PtrToInt RoundTrip Cast To BitCast.
+// Simplifies IntToPtr/PtrToInt RoundTrip Cast.
 // inttoptr ( ptrtoint (x) ) --> x
 Value *InstCombinerImpl::simplifyIntToPtrRoundTripCast(Value *Val) {
   auto *IntToPtr = dyn_cast<IntToPtrInst>(Val);
@@ -373,10 +373,8 @@ Value *InstCombinerImpl::simplifyIntToPtrRoundTripCast(Value *Val) {
         CastTy->getPointerAddressSpace() ==
             PtrToInt->getSrcTy()->getPointerAddressSpace() &&
         DL.getTypeSizeInBits(PtrToInt->getSrcTy()) ==
-            DL.getTypeSizeInBits(PtrToInt->getDestTy())) {
-      return CastInst::CreateBitOrPointerCast(PtrToInt->getOperand(0), CastTy,
-                                              "", PtrToInt);
-    }
+            DL.getTypeSizeInBits(PtrToInt->getDestTy()))
+      return PtrToInt->getOperand(0);
   }
   return nullptr;
 }

diff --git a/llvm/test/Transforms/InstCombine/ptr-int-ptr-icmp.ll b/llvm/test/Transforms/InstCombine/ptr-int-ptr-icmp.ll
index 5249aa4..f23caae 100644 (file)
--- a/llvm/test/Transforms/InstCombine/ptr-int-ptr-icmp.ll
+++ b/llvm/test/Transforms/InstCombine/ptr-int-ptr-icmp.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -passes=instcombine -S -disable-i2p-p2i-opt < %s | FileCheck %s
+; RUN: opt -passes=instcombine -instcombine-infinite-loop-threshold=2 -S -disable-i2p-p2i-opt < %s | FileCheck %s
 
 target datalayout = "e-p:64:64-p1:16:16-p2:32:32:32-p3:64:64:64"
 target triple = "x86_64-unknown-linux-gnu"