[llvm-commits] [llvm] r127465 - in /llvm/trunk: lib/Analysis/ValueTracking.cpp test/Transforms/InstCombine/sext.ll

[Benjamin Kramer]

Author: d0k
Date: Fri Mar 11 08:46:49 2011
New Revision: 127465

URL: http://llvm.org/viewvc/llvm-project?rev=127465&view=rev
Log:
ComputeMaskedBits: sub falls through to add, and sub doesn't have the same overflow semantics as add.

Should fix the selfhost failures that started with r127463.

Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp
    llvm/trunk/test/Transforms/InstCombine/sext.ll

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=127465&r1=127464&r2=127465&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Fri Mar 11 08:46:49 2011
@@ -431,7 +431,8 @@
     }
 
     // Are we still trying to solve for the sign bit?
-    if (Mask.isNegative() && !KnownZero.isNegative() && !KnownOne.isNegative()){
+    if (I->getOpcode() == Instruction::Add &&
+        Mask.isNegative() && !KnownZero.isNegative() && !KnownOne.isNegative()){
       OverflowingBinaryOperator *OBO = cast<OverflowingBinaryOperator>(I);
       if (OBO->hasNoSignedWrap()) {
         // Adding two positive numbers can't wrap into negative ...

Modified: llvm/trunk/test/Transforms/InstCombine/sext.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/sext.ll?rev=127465&r1=127464&r2=127465&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/sext.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/sext.ll Fri Mar 11 08:46:49 2011
@@ -126,3 +126,13 @@
 ; CHECK-NEXT: store <2 x i16>
 ; CHECK-NEXT: ret
 }                                                                                                                               
+
+define i64 @test12(i32 %x) nounwind {
+  %shr = lshr i32 %x, 1
+  %sub = sub nsw i32 0, %shr
+  %conv = sext i32 %sub to i64
+  ret i64 %conv
+; CHECK: @test12
+; CHECK: sext
+; CHECK: ret
+}