[PATCH] D125352: [InstCombine] fix sub(add(X,Y),umin(Y,Z)) --> add(X,usub.sat(Y,Z))

[Chenbing.Zheng via Phabricator via llvm-commits]

Chenbing.Zheng created this revision.
Chenbing.Zheng added reviewers: nlopes, RKSimon, spatel.
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This patch fix bug left in D124503 <https://reviews.llvm.org/D124503>.
We should do
sub(add(X,Z),umin(Y,Z)) --> add(X,usub.sat(Z,Y))
instead of
sub(add(X,Z),umin(Y,Z)) --> add(X,usub.sat(Y,Z)).

I forget to update sub-minmax.ll in D124503 <https://reviews.llvm.org/D124503>,  
[[TMP1:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[Y:%.*]], i8 [[Z:%.*]]) and 
[[TMP1:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[Z:%.*]], i8 [[Y:%.*]]) can both pass llvm-lit test.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125352

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
  llvm/test/Transforms/InstCombine/sub-minmax.ll


Index: llvm/test/Transforms/InstCombine/sub-minmax.ll
===================================================================
--- llvm/test/Transforms/InstCombine/sub-minmax.ll
+++ llvm/test/Transforms/InstCombine/sub-minmax.ll
@@ -715,9 +715,7 @@
   ret i8 %s
 }
 
-;
-; TODO: sub(add(X,Y),umin(Y,Z)) --> add(X,usubsat(Y,Z))
-;
+; sub(add(X,Y),umin(Y,Z)) --> add(X,usubsat(Y,Z))
 
 define i8 @sub_add_umin(i8 %x, i8 %y, i8 %z) {
 ; CHECK-LABEL: @sub_add_umin(
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -2031,14 +2031,17 @@
 
     {
       // sub(add(X,Y),umin(Y,Z)) --> add(X,usub.sat(Y,Z))
-      // sub(add(X,Z),umin(Y,Z)) --> add(X,usub.sat(Y,Z))
+      // sub(add(X,Z),umin(Y,Z)) --> add(X,usub.sat(Z,Y))
       Value *X, *Y, *Z;
-      if (match(Op1, m_OneUse(m_UMin(m_Value(Y), m_Value(Z)))) &&
-          (match(Op0, m_OneUse(m_c_Add(m_Specific(Y), m_Value(X)))) ||
-           match(Op0, m_OneUse(m_c_Add(m_Specific(Z), m_Value(X)))))) {
-        Value *USub =
-            Builder.CreateIntrinsic(Intrinsic::usub_sat, I.getType(), {Y, Z});
-        return BinaryOperator::CreateAdd(X, USub);
+      if (match(Op1, m_OneUse(m_UMin(m_Value(Y), m_Value(Z))))) {
+        if (match(Op0, m_OneUse(m_c_Add(m_Specific(Y), m_Value(X)))))
+          return BinaryOperator::CreateAdd(
+              X, Builder.CreateIntrinsic(Intrinsic::usub_sat, I.getType(),
+                                         {Y, Z}));
+        if (match(Op0, m_OneUse(m_c_Add(m_Specific(Z), m_Value(X)))))
+          return BinaryOperator::CreateAdd(
+              X, Builder.CreateIntrinsic(Intrinsic::usub_sat, I.getType(),
+                                         {Z, Y}));
       }
     }
   }


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