[IR] add optional parameter for copying IR flags to compare instructions

As shown, this is used to eliminate redundant code in InstCombine,
and there are more cases where we should be using this pattern, but
we're currently unintentionally dropping flags. 

llvm-svn: 346282

1 files changed, 14 insertions, 29 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 2381e26a1d8..c6dbfd92844 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -5281,11 +5281,7 @@ static Instruction *foldFCmpReciprocalAndZero(FCmpInst &I, Instruction *LHSI,
   if (C->isNegative())
     Pred = I.getSwappedPredicate();
 
-  // Finally emit the new fcmp.
-  Value *X = LHSI->getOperand(1);
-  FCmpInst *NewFCI = new FCmpInst(Pred, X, RHSC);
-  NewFCI->copyFastMathFlags(&I);
-  return NewFCI;
+  return new FCmpInst(Pred, LHSI->getOperand(1), RHSC, "", &I);
 }
 
 /// Optimize fabs(X) compared with zero.
@@ -5434,43 +5430,34 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
             if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
               return Res;
       break;
-    case Instruction::Call:
-      if (Instruction *X = foldFabsWithFcmpZero(I))
-        return X;
-      break;
   }
   }
 
+  if (Instruction *R = foldFabsWithFcmpZero(I))
+    return R;
+
   Value *X, *Y;
   if (match(Op0, m_FNeg(m_Value(X)))) {
-    if (match(Op1, m_FNeg(m_Value(Y)))) {
-      // fcmp pred (fneg X), (fneg Y) -> fcmp swap(pred) X, Y
-      Instruction *NewFCmp = new FCmpInst(I.getSwappedPredicate(), X, Y);
-      NewFCmp->copyFastMathFlags(&I);
-      return NewFCmp;
-    }
+    // fcmp pred (fneg X), (fneg Y) -> fcmp swap(pred) X, Y
+    if (match(Op1, m_FNeg(m_Value(Y))))
+      return new FCmpInst(I.getSwappedPredicate(), X, Y, "", &I);
 
+    // fcmp pred (fneg X), C --> fcmp swap(pred) X, -C
     Constant *C;
     if (match(Op1, m_Constant(C))) {
-      // fcmp pred (fneg X), C --> fcmp swap(pred) X, -C
       Constant *NegC = ConstantExpr::getFNeg(C);
-      Instruction *NewFCmp = new FCmpInst(I.getSwappedPredicate(), X, NegC);
-      NewFCmp->copyFastMathFlags(&I);
-      return NewFCmp;
+      return new FCmpInst(I.getSwappedPredicate(), X, NegC, "", &I);
     }
   }
 
   if (match(Op0, m_FPExt(m_Value(X)))) {
-    if (match(Op1, m_FPExt(m_Value(Y))) && X->getType() == Y->getType()) {
-      // fcmp (fpext X), (fpext Y) -> fcmp X, Y
-      Instruction *NewFCmp = new FCmpInst(Pred, X, Y);
-      NewFCmp->copyFastMathFlags(&I);
-      return NewFCmp;
-    }
+    // fcmp (fpext X), (fpext Y) -> fcmp X, Y
+    if (match(Op1, m_FPExt(m_Value(Y))) && X->getType() == Y->getType())
+      return new FCmpInst(Pred, X, Y, "", &I);
 
+    // fcmp (fpext X), C -> fcmp X, (fptrunc C) if fptrunc is lossless
     const APFloat *C;
     if (match(Op1, m_APFloat(C))) {
-      // fcmp (fpext X), C -> fcmp X, (fptrunc C) if fptrunc is lossless
       const fltSemantics &FPSem =
           X->getType()->getScalarType()->getFltSemantics();
       bool Lossy;
@@ -5485,9 +5472,7 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
           ((Fabs.compare(APFloat::getSmallestNormalized(FPSem)) !=
             APFloat::cmpLessThan) || Fabs.isZero())) {
         Constant *NewC = ConstantFP::get(X->getType(), TruncC);
-        Instruction *NewFCmp = new FCmpInst(Pred, X, NewC);
-        NewFCmp->copyFastMathFlags(&I);
-        return NewFCmp;
+        return new FCmpInst(Pred, X, NewC, "", &I);
       }
     }
   }