Fix for PR2479: correctly optimize expressions like (a > 13) & (a ==

15).

See also PR1800, which is about the signed case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52608 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 54e611d2a1edb10c34c1fc1a2b47f02c3a719b64..37637bbe63b86efb06eee8c0c3c890db14b3333e 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -3691,8 +3691,7 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
           case ICmpInst::ICMP_UGT:
             switch (RHSCC) {
             default: assert(0 && "Unknown integer condition code!");
-            case ICmpInst::ICMP_EQ:         // (X u> 13 & X == 15) -> X > 13
-              return ReplaceInstUsesWith(I, LHS);
+            case ICmpInst::ICMP_EQ:         // (X u> 13 & X == 15) -> X == 15
             case ICmpInst::ICMP_UGT:        // (X u> 13 & X u> 15) -> X u> 15
               return ReplaceInstUsesWith(I, RHS);
             case ICmpInst::ICMP_SGT:        // (X u> 13 & X s> 15) -> no change

diff --git a/test/Transforms/InstCombine/2008-06-21-CompareMiscomp.ll b/test/Transforms/InstCombine/2008-06-21-CompareMiscomp.ll
new file mode 100644 (file)
index 0000000..e2d7100
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-06-21-CompareMiscomp.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {icmp eq i32 %In, 15}
+; PR2479
+; (See also PR1800.)
+
+define i1 @test(i32 %In) {
+       %c1 = icmp ugt i32 %In, 13
+       %c2 = icmp eq i32 %In, 15
+       %V = and i1 %c1, %c2
+       ret i1 %V
+}
+