[PATCH] D101210: [InstCombine] ctpop(X) + ctpop(Y) => ctpop(X | Y) if X and Y have no common bits (PR48999)

[Dávid Bolvanský via Phabricator via llvm-commits]

xbolva00 created this revision.
xbolva00 added reviewers: spatel, RKSimon.
Herald added a subscriber: hiraditya.
xbolva00 requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101210

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


Index: llvm/test/Transforms/InstCombine/ctpop.ll
===================================================================
--- llvm/test/Transforms/InstCombine/ctpop.ll
+++ llvm/test/Transforms/InstCombine/ctpop.ll
@@ -203,11 +203,7 @@
 
 define i32 @ctpop_add_no_common_bits(i32 %a, i32 %b) {
 ; CHECK-LABEL: @ctpop_add_no_common_bits(
-; CHECK-NEXT:    [[SHL16:%.*]] = shl i32 [[B:%.*]], 16
-; CHECK-NEXT:    [[CTPOP1:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[SHL16]]), !range [[RNG3:![0-9]+]]
-; CHECK-NEXT:    [[LSHL16:%.*]] = lshr i32 [[B]], 16
-; CHECK-NEXT:    [[CTPOP2:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[LSHL16]]), !range [[RNG3]]
-; CHECK-NEXT:    [[RES:%.*]] = add nuw nsw i32 [[CTPOP1]], [[CTPOP2]]
+; CHECK-NEXT:    [[RES:%.*]] = call i32 @llvm.fshl.i32(i32 [[B:%.*]], i32 [[B]], i32 16)
 ; CHECK-NEXT:    ret i32 [[RES]]
 ;
   %shl16 = shl i32 %b, 16
@@ -220,11 +216,7 @@
 
 define <2 x i32> @ctpop_add_no_common_bits_vec(<2 x i32> %a, <2 x i32> %b) {
 ; CHECK-LABEL: @ctpop_add_no_common_bits_vec(
-; CHECK-NEXT:    [[SHL16:%.*]] = shl <2 x i32> [[A:%.*]], <i32 16, i32 16>
-; CHECK-NEXT:    [[CTPOP1:%.*]] = tail call <2 x i32> @llvm.ctpop.v2i32(<2 x i32> [[SHL16]])
-; CHECK-NEXT:    [[LSHL16:%.*]] = lshr <2 x i32> [[B:%.*]], <i32 16, i32 16>
-; CHECK-NEXT:    [[CTPOP2:%.*]] = tail call <2 x i32> @llvm.ctpop.v2i32(<2 x i32> [[LSHL16]])
-; CHECK-NEXT:    [[RES:%.*]] = add nuw nsw <2 x i32> [[CTPOP1]], [[CTPOP2]]
+; CHECK-NEXT:    [[RES:%.*]] = call <2 x i32> @llvm.fshl.v2i32(<2 x i32> [[A:%.*]], <2 x i32> [[B:%.*]], <2 x i32> <i32 16, i32 16>)
 ; CHECK-NEXT:    ret <2 x i32> [[RES]]
 ;
   %shl16 = shl <2 x i32> %a, <i32 16, i32 16>
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1448,6 +1448,13 @@
         Builder.CreateIntrinsic(Intrinsic::umax, {I.getType()}, {A, B}));
   }
 
+  // ctpop(A) + ctpop(B) => ctpop(A | B) if A and B have no bits set in common.
+  if (match(&I,
+            m_c_BinOp(m_OneUse(m_Intrinsic<Intrinsic::ctpop>(m_Value(A))),
+                      m_OneUse(m_Intrinsic<Intrinsic::ctpop>(m_Value(B))))) &&
+      haveNoCommonBitsSet(A, B, DL, &AC, &I, &DT))
+    return BinaryOperator::CreateOr(A, B);
+
   return Changed ? &I : nullptr;
 }
 


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