[PATCH] D60497: [InstCombine] Handle saddo always overflow

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: lebedev.ri, spatel.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

Followup to D60483 <https://reviews.llvm.org/D60483>: Handle always overflow condition for saddo.


Repository:
  rL LLVM

https://reviews.llvm.org/D60497

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/with_overflow.ll


Index: llvm/test/Transforms/InstCombine/with_overflow.ll
===================================================================
--- llvm/test/Transforms/InstCombine/with_overflow.ll
+++ llvm/test/Transforms/InstCombine/with_overflow.ll
@@ -568,8 +568,9 @@
 ; CHECK-LABEL: @sadd_always_overflow(
 ; CHECK-NEXT:    [[C:%.*]] = icmp sgt i8 [[X:%.*]], 100
 ; CHECK-NEXT:    [[Y:%.*]] = select i1 [[C]], i8 [[X]], i8 100
-; CHECK-NEXT:    [[A:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[Y]], i8 28)
-; CHECK-NEXT:    ret { i8, i1 } [[A]]
+; CHECK-NEXT:    [[A:%.*]] = add nuw i8 [[Y]], 28
+; CHECK-NEXT:    [[TMP1:%.*]] = insertvalue { i8, i1 } { i8 undef, i1 true }, i8 [[A]], 0
+; CHECK-NEXT:    ret { i8, i1 } [[TMP1]]
 ;
   %c = icmp sgt i8 %x, 100
   %y = select i1 %c, i8 %x, i8 100
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3973,15 +3973,15 @@
       if (OR == OverflowResult::NeverOverflows)
         return SetResult(Builder.CreateNUWAdd(LHS, RHS), Builder.getFalse(),
                          true);
-
-      if (OR == OverflowResult::AlwaysOverflows)
-        return SetResult(Builder.CreateAdd(LHS, RHS), Builder.getTrue(), true);
     } else {
       OR = computeOverflowForSignedAdd(LHS, RHS, &OrigI);
       if (OR == OverflowResult::NeverOverflows)
         return SetResult(Builder.CreateNSWAdd(LHS, RHS), Builder.getFalse(),
                          true);
     }
+
+    if (OR == OverflowResult::AlwaysOverflows)
+      return SetResult(Builder.CreateAdd(LHS, RHS), Builder.getTrue(), true);
     break;
   }
 


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