[InstCombine] simplify fcmp+select canonicalization; NFCI

We had 2 blocks of code that are nearly identical. Existing
regression tests should cover both of the patterns.

Author: rotateright

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -2333,7 +2333,9 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
 
   // See if we are selecting two values based on a comparison of the two values.
   if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
-    if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
+    Value *Cmp0 = FCI->getOperand(0), *Cmp1 = FCI->getOperand(1);
+    if ((Cmp0 == TrueVal && Cmp1 == FalseVal) ||
+        (Cmp0 == FalseVal && Cmp1 == TrueVal)) {
       // Canonicalize to use ordered comparisons by swapping the select
       // operands.
       //
@@ -2343,25 +2345,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
         FCmpInst::Predicate InvPred = FCI->getInversePredicate();
         IRBuilder<>::FastMathFlagGuard FMFG(Builder);
         Builder.setFastMathFlags(FCI->getFastMathFlags());
-        Value *NewCond = Builder.CreateFCmp(InvPred, TrueVal, FalseVal,
-                                            FCI->getName() + ".inv");
-
-        return SelectInst::Create(NewCond, FalseVal, TrueVal,
-                                  SI.getName() + ".p");
-      }
-
-      // NOTE: if we wanted to, this is where to detect MIN/MAX
-    } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
-      // Canonicalize to use ordered comparisons by swapping the select
-      // operands.
-      //
-      // e.g.
-      // (X ugt Y) ? X : Y -> (X ole Y) ? X : Y
-      if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
-        FCmpInst::Predicate InvPred = FCI->getInversePredicate();
-        IRBuilder<>::FastMathFlagGuard FMFG(Builder);
-        Builder.setFastMathFlags(FCI->getFastMathFlags());
-        Value *NewCond = Builder.CreateFCmp(InvPred, FalseVal, TrueVal,
+        Value *NewCond = Builder.CreateFCmp(InvPred, Cmp0, Cmp1,
                                             FCI->getName() + ".inv");
 
         return SelectInst::Create(NewCond, FalseVal, TrueVal,