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[InstCombine] Simplify (add/sub (sub/add) (sub/add)) irrelevant of use-count #105866

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[InstCombine] Simplify (add/sub (sub/add) (sub/add)) irrelevant of use-count #105866

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b417163
[InstCombine] Add tests for reassosiating `(add/sub (sub/add) (sub/ad…
goldsteinn Aug 22, 2024
73f0712
[InstCombine] Simplify `(add/sub (sub/add) (sub/add))` irrelivant of …
goldsteinn Aug 22, 2024
d16b8d4
Correctly guard foldAddLike for or
goldsteinn Aug 23, 2024
f058c17
Fixups
goldsteinn Aug 24, 2024
6d62821
Make API commutatable
goldsteinn Aug 26, 2024
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33 changes: 33 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1521,6 +1521,12 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
return R;

Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
if (Instruction *R = foldAddLikeCommutative(LHS, RHS, I.hasNoSignedWrap(),
I.hasNoUnsignedWrap()))
return R;
if (Instruction *R = foldAddLikeCommutative(RHS, LHS, I.hasNoSignedWrap(),
I.hasNoUnsignedWrap()))
return R;
Type *Ty = I.getType();
if (Ty->isIntOrIntVectorTy(1))
return BinaryOperator::CreateXor(LHS, RHS);
Expand Down Expand Up @@ -2286,6 +2292,33 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
}
}

{
Value *W, *Z;
if (match(Op0, m_AddLike(m_Value(W), m_Value(X))) &&
match(Op1, m_AddLike(m_Value(Y), m_Value(Z)))) {
Instruction *R = nullptr;
if (W == Y)
R = BinaryOperator::CreateSub(X, Z);
else if (W == Z)
R = BinaryOperator::CreateSub(X, Y);
else if (X == Y)
R = BinaryOperator::CreateSub(W, Z);
else if (X == Z)
R = BinaryOperator::CreateSub(W, Y);
if (R) {
bool NSW = I.hasNoSignedWrap() &&
match(Op0, m_NSWAddLike(m_Value(), m_Value())) &&
match(Op1, m_NSWAddLike(m_Value(), m_Value()));

bool NUW = I.hasNoUnsignedWrap() &&
match(Op1, m_NUWAddLike(m_Value(), m_Value()));
R->setHasNoSignedWrap(NSW);
R->setHasNoUnsignedWrap(NUW);
return R;
}
}
}

// (~X) - (~Y) --> Y - X
{
// Need to ensure we can consume at least one of the `not` instructions,
Expand Down
11 changes: 11 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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Expand Up @@ -3580,6 +3580,17 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
if (Instruction *R = tryFoldInstWithCtpopWithNot(&I))
return R;

if (cast<PossiblyDisjointInst>(I).isDisjoint()) {
if (Instruction *R =
foldAddLikeCommutative(I.getOperand(0), I.getOperand(1),
/*NSW=*/true, /*NUW=*/true))
return R;
if (Instruction *R =
foldAddLikeCommutative(I.getOperand(1), I.getOperand(0),
/*NSW=*/true, /*NUW=*/true))
return R;
}

Value *X, *Y;
const APInt *CV;
if (match(&I, m_c_Or(m_OneUse(m_Xor(m_Value(X), m_APInt(CV))), m_Value(Y))) &&
Expand Down
4 changes: 4 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineInternal.h
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Expand Up @@ -585,6 +585,10 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
FPClassTest DemandedMask, KnownFPClass &Known,
unsigned Depth = 0);

/// Common transforms for add / disjoint or
Instruction *foldAddLikeCommutative(Value *LHS, Value *RHS, bool NSW,
bool NUW);

/// Canonicalize the position of binops relative to shufflevector.
Instruction *foldVectorBinop(BinaryOperator &Inst);
Instruction *foldVectorSelect(SelectInst &Sel);
Expand Down
18 changes: 18 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Expand Up @@ -2008,6 +2008,24 @@ static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) {
return true;
}

Instruction *InstCombinerImpl::foldAddLikeCommutative(Value *LHS, Value *RHS,
bool NSW, bool NUW) {
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Please move this into InstCombineAddSub.cpp. It will make it easier to move folds if necessary.

Value *A, *B, *C;
if (match(LHS, m_Sub(m_Value(A), m_Value(B))) &&
match(RHS, m_Sub(m_Value(C), m_Specific(A)))) {
Instruction *R = BinaryOperator::CreateSub(C, B);
bool NSWOut = NSW && match(LHS, m_NSWSub(m_Value(), m_Value())) &&
match(RHS, m_NSWSub(m_Value(), m_Value()));

bool NUWOut = match(LHS, m_NUWSub(m_Value(), m_Value())) &&
match(RHS, m_NUWSub(m_Value(), m_Value()));
R->setHasNoSignedWrap(NSWOut);
R->setHasNoUnsignedWrap(NUWOut);
return R;
}
return nullptr;
}

Instruction *InstCombinerImpl::foldVectorBinop(BinaryOperator &Inst) {
if (!isa<VectorType>(Inst.getType()))
return nullptr;
Expand Down
207 changes: 207 additions & 0 deletions llvm/test/Transforms/InstCombine/fold-add-sub.ll
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@@ -0,0 +1,207 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

declare void @use.i8(i8)
define i8 @test_add_nsw(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_add_nsw(
; CHECK-NEXT: [[LHS:%.*]] = add nsw i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = add nsw i8 [[X]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub nsw i8 [[Y]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = add nsw i8 %x, %y
%rhs = add nsw i8 %x, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = sub nsw i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_add_nsw_no_prop(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_add_nsw_no_prop(
; CHECK-NEXT: [[LHS:%.*]] = add nsw i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = add nuw i8 [[X]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[Y]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = add nsw i8 %x, %y
%rhs = add nuw i8 %x, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = sub nsw i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_add(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_add(
; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[Y]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = add i8 %x, %y
%rhs = add i8 %x, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = sub i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_add_fail(i8 %w, i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_add_fail(
; CHECK-NEXT: [[LHS:%.*]] = add i8 [[W:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X:%.*]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[LHS]], [[RHS]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = add i8 %w, %y
%rhs = add i8 %x, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = sub i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_add_nuw(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_add_nuw(
; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = or disjoint i8 [[X]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub nuw i8 [[Y]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = add i8 %x, %y
%rhs = or disjoint i8 %x, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = sub nuw i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_add_nuw_no_prop(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_add_nuw_no_prop(
; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = or disjoint i8 [[X]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[Y]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = add i8 %x, %y
%rhs = or disjoint i8 %x, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = sub i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_sub_nuw(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_sub_nuw(
; CHECK-NEXT: [[LHS:%.*]] = sub nuw i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = sub nuw i8 [[Y]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub nuw i8 [[X]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = sub nuw i8 %x, %y
%rhs = sub nuw i8 %y, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = add i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_sub_nuw_no_prop(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_sub_nuw_no_prop(
; CHECK-NEXT: [[LHS:%.*]] = sub nuw i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = sub i8 [[Y]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[X]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = sub nuw i8 %x, %y
%rhs = sub i8 %y, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = add nuw i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_sub_nsw(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_sub_nsw(
; CHECK-NEXT: [[LHS:%.*]] = sub nsw i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = sub nsw i8 [[Y]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub nsw i8 [[X]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = sub nsw i8 %x, %y
%rhs = sub nsw i8 %y, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = or disjoint i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_sub_nsw_no_prop(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_sub_nsw_no_prop(
; CHECK-NEXT: [[LHS:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = sub nsw i8 [[Y]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[X]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = sub i8 %x, %y
%rhs = sub nsw i8 %y, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = or disjoint i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_sub_none(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_sub_none(
; CHECK-NEXT: [[LHS:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = sub i8 [[Y]], [[Z:%.*]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = sub i8 [[X]], [[Z]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = sub i8 %x, %y
%rhs = sub i8 %y, %z
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = add i8 %lhs, %rhs
ret i8 %r
}

define i8 @test_sub_none_fail(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @test_sub_none_fail(
; CHECK-NEXT: [[LHS:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[RHS:%.*]] = sub i8 [[Z:%.*]], [[Y]]
; CHECK-NEXT: call void @use.i8(i8 [[LHS]])
; CHECK-NEXT: call void @use.i8(i8 [[RHS]])
; CHECK-NEXT: [[R:%.*]] = add i8 [[LHS]], [[RHS]]
; CHECK-NEXT: ret i8 [[R]]
;
%lhs = sub i8 %x, %y
%rhs = sub i8 %z, %y
call void @use.i8(i8 %lhs)
call void @use.i8(i8 %rhs)
%r = add i8 %lhs, %rhs
ret i8 %r
}
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