From: Daniel Dunbar <daniel@zuster.org>
Date: Thu, 13 Nov 2008 02:20:34 +0000 (+0000)
Subject: Easy IRgen improvement for bitfields, don't emit x >> 0.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f3edc2fa81b71c32fbc3546be6c0012ff77ec07c;p=clang

Easy IRgen improvement for bitfields, don't emit x >> 0.
 - Logic such as this quite possibly should be optional builder
   behavior.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59213 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 3d8d192a2d..ad2f78b8e7 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -214,8 +214,9 @@ RValue CodeGenFunction::EmitLoadOfBitfieldLValue(LValue LV,
   llvm::Value *Val = Builder.CreateLoad(Ptr, LV.isVolatileQualified(), "tmp");
   
   // Shift to proper location.
-  Val = Builder.CreateLShr(Val, llvm::ConstantInt::get(EltTy, StartBit), 
-                           "bf.lo");
+  if (StartBit)
+    Val = Builder.CreateLShr(Val, llvm::ConstantInt::get(EltTy, StartBit), 
+                             "bf.lo");
   
   // Mask off unused bits.
   llvm::Constant *LowMask =