[PATCH] D136582: [InstCombine] fold `sub + and` pattern with specific const value

[chenglin.bi via Phabricator via llvm-commits]

bcl5980 updated this revision to Diff 472128.
bcl5980 added a comment.

origin version rebased.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D136582/new/

https://reviews.llvm.org/D136582

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


Index: llvm/test/Transforms/InstCombine/sub.ll
===================================================================
--- llvm/test/Transforms/InstCombine/sub.ll
+++ llvm/test/Transforms/InstCombine/sub.ll
@@ -2236,9 +2236,8 @@
 ; C2 is negative pow2
 define i10 @sub_to_and_nuw(i10 %x) {
 ; CHECK-LABEL: @sub_to_and_nuw(
-; CHECK-NEXT:    [[SUB:%.*]] = sub nuw i10 71, [[X:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i10 [[SUB]], 120
-; CHECK-NEXT:    [[R:%.*]] = sub nuw nsw i10 443, [[AND]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i10 [[X:%.*]], 120
+; CHECK-NEXT:    [[R:%.*]] = add nuw nsw i10 [[TMP1]], 379
 ; CHECK-NEXT:    ret i10 [[R]]
 ;
   %sub = sub nuw i10 71, %x
@@ -2253,9 +2252,8 @@
 ; ((C2 + C3) & ((C2 & C3) - 1)) == ((C2 & C3) - 1)
 define i10 @sub_to_and_negpow2(i10 %x) {
 ; CHECK-LABEL: @sub_to_and_negpow2(
-; CHECK-NEXT:    [[SUB:%.*]] = sub i10 71, [[X:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and i10 [[SUB]], -8
-; CHECK-NEXT:    [[R:%.*]] = sub i10 33, [[AND]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i10 [[X:%.*]], -8
+; CHECK-NEXT:    [[R:%.*]] = add i10 [[TMP1]], -31
 ; CHECK-NEXT:    ret i10 [[R]]
 ;
   %sub = sub i10 71, %x
@@ -2342,9 +2340,8 @@
 
 define <2 x i8> @sub_to_and_vector1(<2 x i8> %x) {
 ; CHECK-LABEL: @sub_to_and_vector1(
-; CHECK-NEXT:    [[SUB:%.*]] = sub nuw <2 x i8> <i8 71, i8 71>, [[X:%.*]]
-; CHECK-NEXT:    [[AND:%.*]] = and <2 x i8> [[SUB]], <i8 120, i8 120>
-; CHECK-NEXT:    [[R:%.*]] = sub nsw <2 x i8> <i8 55, i8 55>, [[AND]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i8> [[X:%.*]], <i8 120, i8 120>
+; CHECK-NEXT:    [[R:%.*]] = add nsw <2 x i8> [[TMP1]], <i8 -9, i8 -9>
 ; CHECK-NEXT:    ret <2 x i8> [[R]]
 ;
   %sub = sub nuw <2 x i8> <i8 71, i8 71>, %x
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -2032,12 +2032,34 @@
   }
 
   const APInt *Op0C;
-  if (match(Op0, m_APInt(Op0C)) && Op0C->isMask()) {
-    // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known
-    // zero.
-    KnownBits RHSKnown = computeKnownBits(Op1, 0, &I);
-    if ((*Op0C | RHSKnown.Zero).isAllOnes())
-      return BinaryOperator::CreateXor(Op1, Op0);
+  if (match(Op0, m_APInt(Op0C))) {
+    if (Op0C->isMask()) {
+      // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known
+      // zero.
+      KnownBits RHSKnown = computeKnownBits(Op1, 0, &I);
+      if ((*Op0C | RHSKnown.Zero).isAllOnes())
+        return BinaryOperator::CreateXor(Op1, Op0);
+    }
+
+    // C - ((C3 -nuw X) & C2) --> (C - (C2 & C3)) + (X & C2) when:
+    // (C3 - (C2 & C3) + 1) is pow2
+    // ((C2 + C3) & ((C2 & C3) - 1)) == ((C2 & C3) - 1)
+    // C2 is negative pow2 || sub nuw
+    const APInt *C2, *C3;
+    BinaryOperator *InnerSub;
+    if (match(Op1, m_OneUse(m_And(m_BinOp(InnerSub), m_APInt(C2)))) &&
+        match(InnerSub, m_Sub(m_APInt(C3), m_Value(X)))) {
+      APInt C2AndC3 = *C2 & *C3;
+      APInt C2AndC3Minus1 = C2AndC3 - 1;
+      APInt C2AddC3 = *C2 + *C3;
+      if ((InnerSub->hasNoUnsignedWrap() || C2->isNegatedPowerOf2()) &&
+          (*C3 - C2AndC3Minus1).isPowerOf2() &&
+          C2AndC3Minus1.isSubsetOf(C2AddC3)) {
+        Value *And = Builder.CreateAnd(X, ConstantInt::get(I.getType(), *C2));
+        return BinaryOperator::CreateAdd(
+            And, ConstantInt::get(I.getType(), *Op0C - C2AndC3));
+      }
+    }
   }
 
   {


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