[llvm-commits] [llvm] r134379 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCompares.cpp test/Transforms/InstCombine/icmp.ll

[Benjamin Kramer]

Author: d0k
Date: Mon Jul  4 15:16:36 2011
New Revision: 134379

URL: http://llvm.org/viewvc/llvm-project?rev=134379&view=rev
Log:
PR10267: Don't combine an equality compare with an AND into an inequality compare when the AND has more than one use.

This can pessimize code, inequalities are generally more expensive.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/icmp.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=134379&r1=134378&r2=134379&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Mon Jul  4 15:16:36 2011
@@ -1454,7 +1454,11 @@
             return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ :
                                 ICmpInst::ICMP_NE, LHSI,
                                 Constant::getNullValue(RHS->getType()));
-          
+
+          // Don't perform the following transforms if the AND has multiple uses
+          if (!BO->hasOneUse())
+            break;
+
           // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
           if (BOC->getValue().isSignBit()) {
             Value *X = BO->getOperand(0);

Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=134379&r1=134378&r2=134379&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Mon Jul  4 15:16:36 2011
@@ -547,3 +547,15 @@
   %cmp = icmp eq i32 %sub, 123
   ret i1 %cmp
 }
+
+; PR10267 Don't make icmps more expensive when no other inst is subsumed.
+declare void @foo(i32)
+; CHECK: @test57
+; CHECK: %and = and i32 %a, -2
+; CHECK: %cmp = icmp ne i32 %and, 0
+define i1 @test57(i32 %a) {
+  %and = and i32 %a, -2
+  %cmp = icmp ne i32 %and, 0
+  call void @foo(i32 %and)
+  ret i1 %cmp
+}