[llvm-commits] [llvm] r96432 - in /llvm/trunk: lib/Analysis/ConstantFolding.cpp test/Transforms/InstCombine/bswap-fold.ll

[Dan Gohman]

Author: djg
Date: Tue Feb 16 18:54:58 2010
New Revision: 96432

URL: http://llvm.org/viewvc/llvm-project?rev=96432&view=rev
Log:
Fold bswap(undef) to undef.

Modified:
    llvm/trunk/lib/Analysis/ConstantFolding.cpp
    llvm/trunk/test/Transforms/InstCombine/bswap-fold.ll

Modified: llvm/trunk/lib/Analysis/ConstantFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ConstantFolding.cpp?rev=96432&r1=96431&r2=96432&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp (original)
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp Tue Feb 16 18:54:58 2010
@@ -1179,6 +1179,12 @@
       return 0;
     }
     
+    if (isa<UndefValue>(Operands[0])) {
+      if (Name.startswith("llvm.bswap"))
+        return Operands[0];
+      return 0;
+    }
+
     return 0;
   }
   

Modified: llvm/trunk/test/Transforms/InstCombine/bswap-fold.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/bswap-fold.ll?rev=96432&r1=96431&r2=96432&view=diff

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/bswap-fold.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/bswap-fold.ll Tue Feb 16 18:54:58 2010
@@ -67,3 +67,9 @@
   %D = tail call i16 @llvm.bswap.i16(i16 %C) nounwind
   ret i16 %D
 }
+
+; Misc: Fold bswap(undef) to undef.
+define i64 @foo() {
+  %a = call i64 @llvm.bswap.i64(i64 undef)
+  ret i64 %a
+}