From: Nick Lewycky <nicholas@mxc.ca>
Date: Sun, 20 Sep 2009 06:24:51 +0000 (+0000)
Subject: Teach the constant folder how to not a cmpinst.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=3105ebfaf7105ffe20530a70194fa8d85d07fb7c;p=oota-llvm.git

Teach the constant folder how to not a cmpinst.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82378 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp
index 3f5c7efbb9a..1cf7b290c1e 100644
--- a/lib/VMCore/ConstantFold.cpp
+++ b/lib/VMCore/ConstantFold.cpp
@@ -704,6 +704,20 @@ Constant *llvm::ConstantFoldBinaryInstruction(LLVMContext &Context,
       break;
     case Instruction::Xor:
       if (CI2->equalsInt(0)) return C1;    // X ^ 0 == X
+
+      if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
+        switch (CE1->getOpcode()) {
+        default: break;
+        case Instruction::ICmp:
+        case Instruction::FCmp:
+          // icmp pred ^ true -> icmp !pred
+          assert(CI2->equalsInt(1));
+	  CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
+          pred = CmpInst::getInversePredicate(pred);
+          return ConstantExpr::getCompare(pred, CE1->getOperand(0),
+                                          CE1->getOperand(1));
+        }
+      }
       break;
     case Instruction::AShr:
       // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
diff --git a/test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll b/test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll
index 0a40c0ce2c4..66a3a85b3ce 100644
--- a/test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll
+++ b/test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll
@@ -28,3 +28,9 @@ global i1 icmp ule (i32* bitcast (i8* @X to i32*), i32* bitcast (i8* @Y to i32*)
 ; CHECK-NOT: bitcast
 ; CHECK: icmp
 
+global i1 icmp eq (i1 icmp ult (i8* @X, i8* @Y), i1 false)
+; CHECK-NOT: false
+; CHECK: icmp
+global i1 icmp eq (i1 icmp ult (i8* @X, i8* @Y), i1 true)
+; CHECK-NOT: true
+; CHECK: icmp