[InstCombine] Handle ssubo always overflow

Following D60483 and D60497, this adds support for AlwaysOverflows
handling for ssubo. This is the last case we can handle right now.

Differential Revision: https://reviews.llvm.org/D60518

llvm-svn: 358100

1 files changed, 3 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index bc99b177a7e..2c7d70e4db4 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3997,15 +3997,15 @@ bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
       if (OR == OverflowResult::NeverOverflows)
         return SetResult(Builder.CreateNUWSub(LHS, RHS), Builder.getFalse(),
                          true);
-
-      if (OR == OverflowResult::AlwaysOverflows)
-        return SetResult(Builder.CreateSub(LHS, RHS), Builder.getTrue(), true);
     } else {
       OR = computeOverflowForSignedSub(LHS, RHS, &OrigI);
       if (OR == OverflowResult::NeverOverflows)
         return SetResult(Builder.CreateNSWSub(LHS, RHS), Builder.getFalse(),
                          true);
     }
+
+    if (OR == OverflowResult::AlwaysOverflows)
+      return SetResult(Builder.CreateSub(LHS, RHS), Builder.getTrue(), true);
     break;
   }