[InstCombine] Call getCmpPredicateForMinMax only with a valid SPF

Summary:
There are `SelectPatternFlavor`s that don't represent min or max idioms,
and we should not be passing those to `getCmpPredicateForMinMax`.

Fixes PR25745.

Reviewers: majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D15249

llvm-svn: 254869

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 2baa131bc99..776704d1efa 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1070,7 +1070,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
     SelectPatternResult SPR = matchSelectPattern(&SI, LHS, RHS, &CastOp);
     auto SPF = SPR.Flavor;
 
-    if (SPF) {
+    if (SelectPatternResult::isMinOrMax(SPF)) {
       // Canonicalize so that type casts are outside select patterns.
       if (LHS->getType()->getPrimitiveSizeInBits() !=
           SI.getType()->getPrimitiveSizeInBits()) {
@@ -1091,11 +1091,15 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
                                            SI.getType());
         return ReplaceInstUsesWith(SI, NewSI);
       }
+    }
 
+    if (SPF) {
       // MAX(MAX(a, b), a) -> MAX(a, b)
       // MIN(MIN(a, b), a) -> MIN(a, b)
       // MAX(MIN(a, b), a) -> a
       // MIN(MAX(a, b), a) -> a
+      // ABS(ABS(a)) -> ABS(a)
+      // NABS(NABS(a)) -> NABS(a)
       if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor)
         if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
                                           SI, SPF, RHS))