Add missing newlines at EOF (for clang++).

[oota-llvm.git] / lib / Transforms / Scalar / InstructionCombining.cpp

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 2c73e7ae0fe87360726ca02316e2d1c73bf79bb2..a6e0eef854d4e3b719a423ed54dbe44253e6145f 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -6356,24 +6356,26 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
         // comparison into the select arms, which will cause one to be
         // constant folded and the select turned into a bitwise or.
         Value *Op1 = 0, *Op2 = 0;
-        if (LHSI->hasOneUse()) {
-          if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
-            // Fold the known value into the constant operand.
-            Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
-            // Insert a new ICmp of the other select operand.
-            Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2),
-                                      RHSC, I.getName());
-          } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
-            // Fold the known value into the constant operand.
-            Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
-            // Insert a new ICmp of the other select operand.
+        if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1)))
+          Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
+        if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2)))
+          Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
+
+        // We only want to perform this transformation if it will not lead to
+        // additional code. This is true if either both sides of the select
+        // fold to a constant (in which case the icmp is replaced with a select
+        // which will usually simplify) or this is the only user of the
+        // select (in which case we are trading a select+icmp for a simpler
+        // select+icmp).
+        if ((Op1 && Op2) || (LHSI->hasOneUse() && (Op1 || Op2))) {
+          if (!Op1)
             Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1),
                                       RHSC, I.getName());
-          }
-        }
-
-        if (Op1)
+          if (!Op2)
+            Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2),
+                                      RHSC, I.getName());
           return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
+        }
         break;
       }
       case Instruction::Call:
@@ -7299,19 +7301,17 @@ Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) {
 
   // If the re-extended constant didn't change...
   if (Res2 == CI) {
-    // Make sure that sign of the Cmp and the sign of the Cast are the same.
-    // For example, we might have:
-    //    %A = sext i16 %X to i32
-    //    %B = icmp ugt i32 %A, 1330
-    // It is incorrect to transform this into 
-    //    %B = icmp ugt i16 %X, 1330
-    // because %A may have negative value. 
-    //
-    // However, we allow this when the compare is EQ/NE, because they are
-    // signless.
-    if (isSignedExt == isSignedCmp || ICI.isEquality())
+    // Deal with equality cases early.
+    if (ICI.isEquality())
       return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1);
-    return 0;
+
+    // A signed comparison of sign extended values simplifies into a
+    // signed comparison.
+    if (isSignedExt && isSignedCmp)
+      return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1);
+
+    // The other three cases all fold into an unsigned comparison.
+    return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, Res1);
   }
 
   // The re-extended constant changed so the constant cannot be represented