[llvm-commits] [llvm] r124188 - in /llvm/trunk: lib/Analysis/ValueTracking.cpp test/Transforms/InstSimplify/2011-01-18-Compare.ll

[Duncan Sands]

Author: baldrick
Date: Tue Jan 25 09:14:15 2011
New Revision: 124188

URL: http://llvm.org/viewvc/llvm-project?rev=124188&view=rev
Log:
In which I discover that zero+zero is zero, d'oh!

Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp
    llvm/trunk/test/Transforms/InstSimplify/2011-01-18-Compare.ll

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=124188&r1=124187&r2=124188&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Jan 25 09:14:15 2011
@@ -740,10 +740,10 @@
     ComputeSignBit(Y, YKnownNonNegative, YKnownNegative, TD, Depth);
 
     // If X and Y are both non-negative (as signed values) then their sum is not
-    // zero.
+    // zero unless both X and Y are zero.
     if (XKnownNonNegative && YKnownNonNegative)
-      return false;
-//      return true;
+      if (isKnownNonZero(X, TD, Depth) || isKnownNonZero(Y, TD, Depth))
+        return true;
 
     // If X and Y are both negative (as signed values) then their sum is not
     // zero unless both X and Y equal INT_MIN.

Modified: llvm/trunk/test/Transforms/InstSimplify/2011-01-18-Compare.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/2011-01-18-Compare.ll?rev=124188&r1=124187&r2=124188&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/2011-01-18-Compare.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/2011-01-18-Compare.ll Tue Jan 25 09:14:15 2011
@@ -61,11 +61,14 @@
 }
 
 define i1 @add(i32 %x, i32 %y) {
+; CHECK: @add
   %l = lshr i32 %x, 1
-  %r = lshr i32 %y, 1
+  %q = lshr i32 %y, 1
+  %r = or i32 %q, 1
   %s = add i32 %l, %r
   %c = icmp eq i32 %s, 0
   ret i1 %c
+; CHECK: ret i1 false
 }
 
 define i1 @add2(i8 %x, i8 %y) {
@@ -78,6 +81,16 @@
 ; CHECK: ret i1 false
 }
 
+define i1 @add3(i8 %x, i8 %y) {
+; CHECK: @add3
+  %l = zext i8 %x to i32
+  %r = zext i8 %y to i32
+  %s = add i32 %l, %r
+  %c = icmp eq i32 %s, 0
+  ret i1 %c
+; CHECK: ret i1 %c
+}
+
 define i1 @addpowtwo(i32 %x, i32 %y) {
 ; CHECK: @addpowtwo
   %l = lshr i32 %x, 1