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.

llvm-svn: 134379

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -1455,6 +1455,10 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
                                 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);

llvm/test/Transforms/InstCombine/icmp.ll

@@ -547,3 +547,15 @@ define i1 @test56(i32 %a) {
   %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
+}