Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[InstCombine] Fold ((X << nuw Z) binop nuw Y) >>u Z --> X binop nuw (Y >>u Z) #88193

Merged
merged 2 commits into from
May 7, 2024
Merged

[InstCombine] Fold ((X << nuw Z) binop nuw Y) >>u Z --> X binop nuw (Y >>u Z) #88193

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
ae4ad96
[InstCombine] Pre-commit tests (NFC)
AZero13 May 6, 2024
fb94d49
[InstCombine] Fold ((X << nuw Z) binop nuw Y) >>u Z --> X binop nuw (…
AZero13 May 7, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
50 changes: 48 additions & 2 deletions llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1259,6 +1259,54 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
match(Op1, m_SpecificIntAllowPoison(BitWidth - 1)))
return new ZExtInst(Builder.CreateIsNotNeg(X, "isnotneg"), Ty);

// ((X << nuw Z) sub nuw Y) >>u exact Z --> X sub nuw (Y >>u exact Z),
Value *Y;
if (I.isExact() &&
match(Op0, m_OneUse(m_NUWSub(m_NUWShl(m_Value(X), m_Specific(Op1)),
m_Value(Y))))) {
Value *NewLshr = Builder.CreateLShr(Y, Op1, "", /*isExact=*/true);
auto *NewSub = BinaryOperator::CreateNUWSub(X, NewLshr);
NewSub->setHasNoSignedWrap(
cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap());
return NewSub;
}

auto isSuitableBinOpcode = [](Instruction::BinaryOps BinOpcode) {
switch (BinOpcode) {
default:
return false;
case Instruction::Add:
case Instruction::And:
AZero13 marked this conversation as resolved.
Show resolved Hide resolved
case Instruction::Or:
case Instruction::Xor:
// And does not work here, and sub is handled separately.
return true;
}
};

// If both the binop and the shift are nuw, then:
// ((X << nuw Z) binop nuw Y) >>u Z --> X binop nuw (Y >>u Z)
AZero13 marked this conversation as resolved.
Show resolved Hide resolved
if (match(Op0, m_OneUse(m_c_BinOp(m_NUWShl(m_Value(X), m_Specific(Op1)),
m_Value(Y))))) {
BinaryOperator *Op0OB = cast<BinaryOperator>(Op0);
if (isSuitableBinOpcode(Op0OB->getOpcode())) {
if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(Op0);
!OBO || OBO->hasNoUnsignedWrap()) {
Value *NewLshr = Builder.CreateLShr(
Y, Op1, "", I.isExact() && Op0OB->getOpcode() != Instruction::And);
auto *NewBinOp = BinaryOperator::Create(Op0OB->getOpcode(), NewLshr, X);
if (OBO) {
NewBinOp->setHasNoUnsignedWrap(true);
NewBinOp->setHasNoSignedWrap(OBO->hasNoSignedWrap());
} else if (auto *Disjoint = dyn_cast<PossiblyDisjointInst>(Op0)) {
cast<PossiblyDisjointInst>(NewBinOp)->setIsDisjoint(
Disjoint->isDisjoint());
}
return NewBinOp;
}
}
}
AZero13 marked this conversation as resolved.
Show resolved Hide resolved

if (match(Op1, m_APInt(C))) {
unsigned ShAmtC = C->getZExtValue();
auto *II = dyn_cast<IntrinsicInst>(Op0);
Expand All @@ -1275,7 +1323,6 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
return new ZExtInst(Cmp, Ty);
}

Value *X;
const APInt *C1;
if (match(Op0, m_Shl(m_Value(X), m_APInt(C1))) && C1->ult(BitWidth)) {
if (C1->ult(ShAmtC)) {
Expand Down Expand Up @@ -1320,7 +1367,6 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
// ((X << C) + Y) >>u C --> (X + (Y >>u C)) & (-1 >>u C)
// TODO: Consolidate with the more general transform that starts from shl
// (the shifts are in the opposite order).
Value *Y;
if (match(Op0,
m_OneUse(m_c_Add(m_OneUse(m_Shl(m_Value(X), m_Specific(Op1))),
m_Value(Y))))) {
Expand Down
240 changes: 240 additions & 0 deletions llvm/test/Transforms/InstCombine/lshr.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -163,6 +163,17 @@ define <2 x i8> @lshr_exact_splat_vec(<2 x i8> %x) {
ret <2 x i8> %lshr
}

define <2 x i8> @lshr_exact_splat_vec_nuw(<2 x i8> %x) {
; CHECK-LABEL: @lshr_exact_splat_vec_nuw(
; CHECK-NEXT: [[LSHR:%.*]] = add nuw <2 x i8> [[X:%.*]], <i8 1, i8 1>
; CHECK-NEXT: ret <2 x i8> [[LSHR]]
;
%shl = shl nuw <2 x i8> %x, <i8 2, i8 2>
%add = add nuw <2 x i8> %shl, <i8 4, i8 4>
%lshr = lshr <2 x i8> %add, <i8 2, i8 2>
ret <2 x i8> %lshr
}

define i8 @shl_add(i8 %x, i8 %y) {
; CHECK-LABEL: @shl_add(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i8 [[Y:%.*]], 2
Expand Down Expand Up @@ -360,8 +371,222 @@ define <3 x i14> @mul_splat_fold_vec(<3 x i14> %x) {
ret <3 x i14> %t
}

define i32 @shl_add_lshr_flag_preservation(i32 %x, i32 %c, i32 %y) {
AZero13 marked this conversation as resolved.
Show resolved Hide resolved
; CHECK-LABEL: @shl_add_lshr_flag_preservation(
; CHECK-NEXT: [[TMP1:%.*]] = lshr exact i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = add nuw nsw i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%add = add nuw nsw i32 %shl, %y
%lshr = lshr exact i32 %add, %c
ret i32 %lshr
}

AZero13 marked this conversation as resolved.
Show resolved Hide resolved
define i32 @shl_add_lshr(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_add_lshr(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = add nuw i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%add = add nuw i32 %shl, %y
%lshr = lshr i32 %add, %c
ret i32 %lshr
}

define i32 @shl_add_lshr_comm(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_add_lshr_comm(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = add nuw i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%add = add nuw i32 %y, %shl
%lshr = lshr i32 %add, %c
ret i32 %lshr
}
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This test does not actually test the commuted case, because it gets canonicalized, see https://llvm.godbolt.org/z/93sGo78W8.

Read https://llvm.org/docs/InstCombineContributorGuide.html#add-commuted-tests to understand how to resolve this issue.

Also, your pre-commit tests don't show this because your second commit modifies the test inputs as well. The split is to add all tests in the first commit and only change CHECK lines in the second commit. Do not modify test inputs in the second commit.

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This was, once again, not resolved. Your commutative tests are still incorrect.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I'll write another test.


; Negative test

define i32 @shl_add_lshr_no_nuw(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_add_lshr_no_nuw(
; CHECK-NEXT: [[SHL:%.*]] = shl nuw i32 [[X:%.*]], [[C:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[SHL]], [[Y:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 [[ADD]], [[C]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%add = add i32 %shl, %y
%lshr = lshr i32 %add, %c
ret i32 %lshr
}

; Negative test

define i32 @shl_sub_lshr_not_exact(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_sub_lshr_not_exact(
; CHECK-NEXT: [[SHL:%.*]] = shl nuw i32 [[X:%.*]], [[C:%.*]]
; CHECK-NEXT: [[SUB:%.*]] = sub nuw i32 [[SHL]], [[Y:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 [[SUB]], [[C]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%sub = sub nuw i32 %shl, %y
%lshr = lshr i32 %sub, %c
ret i32 %lshr
}

; Negative test

define i32 @shl_sub_lshr_no_nuw(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_sub_lshr_no_nuw(
; CHECK-NEXT: [[SHL:%.*]] = shl nsw i32 [[X:%.*]], [[C:%.*]]
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[SHL]], [[Y:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = lshr exact i32 [[SUB]], [[C]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nsw i32 %x, %c
%sub = sub nsw i32 %shl, %y
%lshr = lshr exact i32 %sub, %c
ret i32 %lshr
}

define i32 @shl_sub_lshr(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_sub_lshr(
; CHECK-NEXT: [[TMP1:%.*]] = lshr exact i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = sub nuw nsw i32 [[X:%.*]], [[TMP1]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%sub = sub nuw nsw i32 %shl, %y
%lshr = lshr exact i32 %sub, %c
ret i32 %lshr
}

define i32 @shl_or_lshr(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_or_lshr(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = or i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%or = or i32 %shl, %y
%lshr = lshr i32 %or, %c
ret i32 %lshr
}

define i32 @shl_or_disjoint_lshr(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_or_disjoint_lshr(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = or disjoint i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%or = or disjoint i32 %shl, %y
%lshr = lshr i32 %or, %c
ret i32 %lshr
}

define i32 @shl_or_lshr_comm(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_or_lshr_comm(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = or i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%or = or i32 %y, %shl
%lshr = lshr i32 %or, %c
ret i32 %lshr
}

define i32 @shl_or_disjoint_lshr_comm(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_or_disjoint_lshr_comm(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = or disjoint i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%or = or disjoint i32 %y, %shl
%lshr = lshr i32 %or, %c
ret i32 %lshr
}

define i32 @shl_xor_lshr(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_xor_lshr(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = xor i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%xor = xor i32 %shl, %y
%lshr = lshr i32 %xor, %c
ret i32 %lshr
}

define i32 @shl_xor_lshr_comm(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_xor_lshr_comm(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = xor i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%xor = xor i32 %y, %shl
%lshr = lshr i32 %xor, %c
ret i32 %lshr
}

define i32 @shl_and_lshr(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_and_lshr(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = and i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%and = and i32 %shl, %y
%lshr = lshr i32 %and, %c
ret i32 %lshr
}

define i32 @shl_and_lshr_comm(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_and_lshr_comm(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[LSHR:%.*]] = and i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[LSHR]]
;
%shl = shl nuw i32 %x, %c
%and = and i32 %y, %shl
%lshr = lshr i32 %and, %c
ret i32 %lshr
}

define i32 @shl_lshr_and_exact(i32 %x, i32 %c, i32 %y) {
; CHECK-LABEL: @shl_lshr_and_exact(
; CHECK-NEXT: [[TMP1:%.*]] = lshr i32 [[Y:%.*]], [[C:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = and i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[TMP2]]
;
%2 = shl nuw i32 %x, %c
%3 = and i32 %2, %y
%4 = lshr exact i32 %3, %c
ret i32 %4
}

; Negative test

AZero13 marked this conversation as resolved.
Show resolved Hide resolved
define i32 @shl_add_lshr_neg(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @shl_add_lshr_neg(
; CHECK-NEXT: [[SHL:%.*]] = shl nuw i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = add nuw nsw i32 [[SHL]], [[Z:%.*]]
; CHECK-NEXT: [[RES:%.*]] = lshr exact i32 [[ADD]], [[Z]]
; CHECK-NEXT: ret i32 [[RES]]
;
%shl = shl nuw i32 %x, %y
%add = add nuw nsw i32 %shl, %z
%res = lshr exact i32 %add, %z
ret i32 %res
}

AZero13 marked this conversation as resolved.
Show resolved Hide resolved
define i32 @mul_splat_fold_wrong_mul_const(i32 %x) {
; CHECK-LABEL: @mul_splat_fold_wrong_mul_const(
; CHECK-NEXT: [[M:%.*]] = mul nuw i32 [[X:%.*]], 65538
Expand All @@ -375,6 +600,21 @@ define i32 @mul_splat_fold_wrong_mul_const(i32 %x) {

; Negative test

define i32 @shl_add_lshr_multiuse(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @shl_add_lshr_multiuse(
; CHECK-NEXT: [[SHL:%.*]] = shl nuw i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[ADD:%.*]] = add nuw nsw i32 [[SHL]], [[Z:%.*]]
; CHECK-NEXT: call void @use(i32 [[ADD]])
; CHECK-NEXT: [[RES:%.*]] = lshr exact i32 [[ADD]], [[Z]]
; CHECK-NEXT: ret i32 [[RES]]
;
%shl = shl nuw i32 %x, %y
%add = add nuw nsw i32 %shl, %z
call void @use (i32 %add)
%res = lshr exact i32 %add, %z
ret i32 %res
}

define i32 @mul_splat_fold_wrong_lshr_const(i32 %x) {
; CHECK-LABEL: @mul_splat_fold_wrong_lshr_const(
; CHECK-NEXT: [[M:%.*]] = mul nuw i32 [[X:%.*]], 65537
Expand Down
Loading