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[InstCombine] Fold (select (icmp eq (and x, y), 0), (add/xor x, y), F) #121841

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[InstCombine] Fold (select (icmp eq (and x, y), 0), (add/xor x, y), F) #121841

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9423bd0
[InstCombine] Add tests for folding `(select (icmp eq (and x, y), 0),…
goldsteinn Jan 6, 2025
ed6e432
[InstCombine] Fold `(select (icmp eq (and x, y), 0), (add/xor x, y), F)`
goldsteinn Jan 6, 2025
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26 changes: 26 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4395,5 +4395,31 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
return replaceOperand(SI, 2, ConstantInt::get(FalseVal->getType(), 0));
}

{
// (select (icmp eq (and X, Y), 0), (add/xor X, Y), F)
// -> (select (icmp eq (and X, Y), 0), (or X, Y), F)
// And vice versa for `ne` pred.
CmpPredicate Pred;
Value *X, *Y;
if (match(CondVal, m_ICmp(Pred, m_And(m_Value(X), m_Value(Y)), m_Zero())) &&
ICmpInst::isEquality(Pred)) {
unsigned RepIdx;
Value *RepArm;
if (Pred == CmpInst::ICMP_EQ) {
RepIdx = 1;
RepArm = TrueVal;
} else {
RepIdx = 2;
RepArm = FalseVal;
}
auto ReduceToOrNoCommonBits =
m_CombineOr(m_c_Xor(m_Specific(X), m_Specific(Y)),
m_c_Add(m_Specific(X), m_Specific(Y)));

if (RepArm->hasOneUse() && match(RepArm, ReduceToOrNoCommonBits))
return replaceOperand(SI, RepIdx, Builder.CreateOr(X, Y));
}
}

return nullptr;
}
45 changes: 39 additions & 6 deletions llvm/test/Transforms/InstCombine/select.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,9 @@

target datalayout = "e-p:64:64-p1:16:16-p2:32:32:32-p3:64:64:64"

declare void @use.i1(i1)
declare void @use.i32(i32)

define i1 @test5(i1 %C) {
; CHECK-LABEL: @test5(
; CHECK-NEXT: [[NOT_C:%.*]] = xor i1 [[C:%.*]], true
Expand Down Expand Up @@ -3784,12 +3787,8 @@ entry:
define i32 @src_and_eq_0_xor_or(i32 %x, i32 %y) {
; CHECK-LABEL: @src_and_eq_0_xor_or(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[AND:%.*]] = and i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[AND]], 0
; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[Y]], [[X]]
; CHECK-NEXT: [[OR:%.*]] = or i32 [[Y]], [[X]]
; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP]], i32 [[XOR]], i32 [[OR]]
; CHECK-NEXT: ret i32 [[COND]]
; CHECK-NEXT: [[OR:%.*]] = or i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: ret i32 [[OR]]
;
entry:
%and = and i32 %y, %x
Expand Down Expand Up @@ -4425,17 +4424,51 @@ define i32 @src_no_trans_select_and_eq0_xor_and(i32 %x, i32 %y) {
; CHECK-LABEL: @src_no_trans_select_and_eq0_xor_and(
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[AND0:%.*]] = icmp eq i32 [[AND]], 0
; CHECK-NEXT: [[XOR:%.*]] = or i32 [[X]], [[Y]]
; CHECK-NEXT: [[COND:%.*]] = select i1 [[AND0]], i32 [[XOR]], i32 [[AND]]
; CHECK-NEXT: ret i32 [[COND]]
;
%and = and i32 %x, %y
%and0 = icmp eq i32 %and, 0
%xor = xor i32 %x, %y
%cond = select i1 %and0, i32 %xor, i32 %and
ret i32 %cond
}

define i32 @src_no_trans_select_and_eq0_xor_and_fail_multiuse(i32 %x, i32 %y) {
; CHECK-LABEL: @src_no_trans_select_and_eq0_xor_and_fail_multiuse(
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[AND0:%.*]] = icmp eq i32 [[AND]], 0
; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X]], [[Y]]
; CHECK-NEXT: call void @use.i32(i32 [[XOR]])
; CHECK-NEXT: [[COND:%.*]] = select i1 [[AND0]], i32 [[XOR]], i32 [[AND]]
; CHECK-NEXT: ret i32 [[COND]]
;
%and = and i32 %x, %y
%and0 = icmp eq i32 %and, 0
%xor = xor i32 %x, %y
call void @use.i32(i32 %xor)
%cond = select i1 %and0, i32 %xor, i32 %and
ret i32 %cond
}

define i32 @src_no_trans_select_and_eq0_add(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @src_no_trans_select_and_eq0_add(
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[AND0:%.*]] = icmp ne i32 [[AND]], 0
; CHECK-NEXT: call void @use.i1(i1 [[AND0]])
; CHECK-NEXT: [[ADD:%.*]] = or i32 [[X]], [[Y]]
; CHECK-NEXT: [[COND:%.*]] = select i1 [[AND0]], i32 [[Z:%.*]], i32 [[ADD]]
; CHECK-NEXT: ret i32 [[COND]]
;
%and = and i32 %x, %y
%and0 = icmp ne i32 %and, 0
call void @use.i1(i1 %and0)
%add = add i32 %x, %y
%cond = select i1 %and0, i32 %z, i32 %add
ret i32 %cond
}

define i32 @src_no_trans_select_or_eq0_or_and(i32 %x, i32 %y) {
; CHECK-LABEL: @src_no_trans_select_or_eq0_or_and(
; CHECK-NEXT: [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
Expand Down
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