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

For example:

```
int src(unsigned int a, unsigned int b)
{
    return __builtin_popcount(a << 16) + __builtin_popcount(b >> 16);
}

int tgt(unsigned int a, unsigned int b)
{
    return __builtin_popcount((a << 16)  | (b >> 16));
}
```

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D101210
This commit is contained in:
Dávid Bolvanský 2021-04-24 17:44:20 +02:00
parent 38225d6921
commit d4ec8ea19c
2 changed files with 14 additions and 12 deletions
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8
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -1448,6 +1448,14 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
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(LHS, m_OneUse(m_Intrinsic<Intrinsic::ctpop>(m_Value(A)))) &&
match(RHS, m_OneUse(m_Intrinsic<Intrinsic::ctpop>(m_Value(B)))) &&
haveNoCommonBitsSet(A, B, DL, &AC, &I, &DT))
return replaceInstUsesWith(
I, Builder.CreateIntrinsic(Intrinsic::ctpop, {I.getType()},
{Builder.CreateOr(A, B)}));
return Changed ? &I : nullptr;
}

18
llvm/test/Transforms/InstCombine/ctpop.ll
View File

@ -203,12 +203,9 @@ define i32 @ctpop_add(i32 %a, i32 %b) {
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: ret i32 [[RES]]
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @llvm.fshl.i32(i32 [[B:%.*]], i32 [[B]], i32 16)
; CHECK-NEXT: [[TMP2:%.*]] = call i32 @llvm.ctpop.i32(i32 [[TMP1]]), !range [[RNG1]]
; CHECK-NEXT: ret i32 [[TMP2]]
;
%shl16 = shl i32 %b, 16
%ctpop1 = tail call i32 @llvm.ctpop.i32(i32 %shl16)
@ -220,12 +217,9 @@ define i32 @ctpop_add_no_common_bits(i32 %a, i32 %b) {
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: ret <2 x i32> [[RES]]
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i32> @llvm.fshl.v2i32(<2 x i32> [[A:%.*]], <2 x i32> [[B:%.*]], <2 x i32> <i32 16, i32 16>)
; CHECK-NEXT: [[TMP2:%.*]] = call <2 x i32> @llvm.ctpop.v2i32(<2 x i32> [[TMP1]])
; CHECK-NEXT: ret <2 x i32> [[TMP2]]
;
%shl16 = shl <2 x i32> %a, <i32 16, i32 16>
%ctpop1 = tail call <2 x i32> @llvm.ctpop.v2i32(<2 x i32> %shl16)