[PATCH] D132412: [InstCombine] reassociate/factor add+mul with common operand

[Sanjay Patel via Phabricator via llvm-commits]

spatel updated this revision to Diff 454824.
spatel edited the summary of this revision.
spatel added a comment.

Patch updated:
Handle a simpler pattern - just looking for a mul with a common operand with an add.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132412/new/

https://reviews.llvm.org/D132412

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


Index: llvm/test/Transforms/InstCombine/add.ll
===================================================================
--- llvm/test/Transforms/InstCombine/add.ll
+++ llvm/test/Transforms/InstCombine/add.ll
@@ -1756,10 +1756,12 @@
   ret i32 %G
 }
 
+; (x * y) + x --> (y + 1) * x
+
 define i8 @mul_add_common_factor_commute1(i8 %x, i8 %y) {
 ; CHECK-LABEL: @mul_add_common_factor_commute1(
-; CHECK-NEXT:    [[M:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[A:%.*]] = add i8 [[M]], [[X]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[Y:%.*]], 1
+; CHECK-NEXT:    [[A:%.*]] = mul i8 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i8 [[A]]
 ;
   %m = mul i8 %x, %y
@@ -1769,8 +1771,8 @@
 
 define <2 x i8> @mul_add_common_factor_commute2(<2 x i8> %x, <2 x i8> %y) {
 ; CHECK-LABEL: @mul_add_common_factor_commute2(
-; CHECK-NEXT:    [[M:%.*]] = mul <2 x i8> [[Y:%.*]], [[X:%.*]]
-; CHECK-NEXT:    [[A:%.*]] = add <2 x i8> [[M]], [[X]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add <2 x i8> [[Y:%.*]], <i8 1, i8 1>
+; CHECK-NEXT:    [[A:%.*]] = mul <2 x i8> [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret <2 x i8> [[A]]
 ;
   %m = mul <2 x i8> %y, %x
@@ -1781,8 +1783,8 @@
 define i8 @mul_add_common_factor_commute3(i8 %p, i8 %y) {
 ; CHECK-LABEL: @mul_add_common_factor_commute3(
 ; CHECK-NEXT:    [[X:%.*]] = mul i8 [[P:%.*]], [[P]]
-; CHECK-NEXT:    [[M:%.*]] = mul i8 [[X]], [[Y:%.*]]
-; CHECK-NEXT:    [[A:%.*]] = add i8 [[X]], [[M]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[Y:%.*]], 1
+; CHECK-NEXT:    [[A:%.*]] = mul i8 [[TMP1]], [[X]]
 ; CHECK-NEXT:    ret i8 [[A]]
 ;
   %x = mul i8 %p, %p ; thwart complexity-based canonicalization
@@ -1795,8 +1797,8 @@
 ; CHECK-LABEL: @mul_add_common_factor_commute4(
 ; CHECK-NEXT:    [[X:%.*]] = mul i8 [[P:%.*]], [[P]]
 ; CHECK-NEXT:    [[Y:%.*]] = mul i8 [[Q:%.*]], [[Q]]
-; CHECK-NEXT:    [[M:%.*]] = mul i8 [[Y]], [[X]]
-; CHECK-NEXT:    [[A:%.*]] = add i8 [[X]], [[M]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[Y]], 1
+; CHECK-NEXT:    [[A:%.*]] = mul i8 [[TMP1]], [[X]]
 ; CHECK-NEXT:    ret i8 [[A]]
 ;
   %x = mul i8 %p, %p ; thwart complexity-based canonicalization
@@ -1806,6 +1808,8 @@
   ret i8 %a
 }
 
+; negative test - extra use
+
 define i8 @mul_add_common_factor_use(i8 %x, i8 %y) {
 ; CHECK-LABEL: @mul_add_common_factor_use(
 ; CHECK-NEXT:    [[M:%.*]] = mul i8 [[X:%.*]], [[Y:%.*]]
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1415,6 +1415,14 @@
     return &I;
   }
 
+  // (X * Y) + X --> (Y + 1) * X
+  Value *X, *Y;
+  if (match(&I, m_c_Add(m_Value(X),
+                        m_OneUse(m_c_Mul(m_Deferred(X), m_Value(Y)))))) {
+    Value *IncY = Builder.CreateAdd(Y, ConstantInt::get(I.getType(), 1));
+    return BinaryOperator::CreateMul(IncY, X);
+  }
+
   // TODO(jingyue): Consider willNotOverflowSignedAdd and
   // willNotOverflowUnsignedAdd to reduce the number of invocations of
   // computeKnownBits.


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