[PATCH] D31683: [InstCombine] Support folding of add instructions with vector constants into select operations

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.

We currently only fold scalar add of constants into selects. This improves this to support vectors too.


https://reviews.llvm.org/D31683

Files:
  lib/Transforms/InstCombine/InstCombineAddSub.cpp
  test/Transforms/InstCombine/add.ll


Index: test/Transforms/InstCombine/add.ll
===================================================================
--- test/Transforms/InstCombine/add.ll
+++ test/Transforms/InstCombine/add.ll
@@ -578,8 +578,7 @@
 
 define <2 x i32> @test42vec(i1 %C) {
 ; CHECK-LABEL: @test42vec(
-; CHECK-NEXT:    [[A:%.*]] = select i1 [[C:%.*]], <2 x i32> <i32 1000, i32 1000>, <2 x i32> <i32 10, i32 10>
-; CHECK-NEXT:    [[V:%.*]] = add nuw nsw <2 x i32> [[A]], <i32 123, i32 123>
+; CHECK-NEXT:    [[V:%.*]] = select i1 [[C:%.*]], <2 x i32> <i32 1123, i32 1123>, <2 x i32> <i32 133, i32 133>
 ; CHECK-NEXT:    ret <2 x i32> [[V]]
 ;
   %A = select i1 %C, <2 x i32> <i32 1000, i32 1000>, <2 x i32> <i32 10, i32 10>
@@ -589,8 +588,7 @@
 
 define <2 x i32> @test42vec2(i1 %C) {
 ; CHECK-LABEL: @test42vec2(
-; CHECK-NEXT:    [[A:%.*]] = select i1 [[C:%.*]], <2 x i32> <i32 1000, i32 2500>, <2 x i32> <i32 10, i32 30>
-; CHECK-NEXT:    [[V:%.*]] = add nuw nsw <2 x i32> [[A]], <i32 123, i32 333>
+; CHECK-NEXT:    [[V:%.*]] = select i1 [[C:%.*]], <2 x i32> <i32 1123, i32 2833>, <2 x i32> <i32 133, i32 363>
 ; CHECK-NEXT:    ret <2 x i32> [[V]]
 ;
   %A = select i1 %C, <2 x i32> <i32 1000, i32 2500>, <2 x i32> <i32 10, i32 30>
Index: lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1128,8 +1128,8 @@
     }
   }
 
-  if (isa<Constant>(RHS) && isa<PHINode>(LHS))
-    if (Instruction *NV = FoldOpIntoPhi(I))
+  if (isa<Constant>(RHS))
+    if (Instruction *NV = foldOpWithConstantIntoOperand(I))
       return NV;
 
   if (I.getType()->getScalarType()->isIntegerTy(1))
@@ -1200,11 +1200,6 @@
         return BinaryOperator::CreateAnd(NewAdd, C2);
       }
     }
-
-    // Try to fold constant add into select arguments.
-    if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
-      if (Instruction *R = FoldOpIntoSelect(I, SI))
-        return R;
   }
 
   // add (select X 0 (sub n A)) A  -->  select X A n


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