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[InstCombine] extend vector select matching for non-splat constants 

In D21740, we discussed trying to make this a more general matcher. However, I didn't see a clean
way to handle the regular m_Not cases and these non-splat vector patterns, so I've opted for the
direct approach here. If there are other potential uses of areInverseVectorBitmasks(), we could
move that helper function to a higher level.

There is an open question as to which is of these forms should be considered the canonical IR:
  %sel = select <4 x i1> <i1 true, i1 false, i1 false, i1 true>, <4 x i32> %a, <4 x i32> %b
  %shuf = shufflevector <4 x i32> %a, <4 x i32> %b, <4 x i32> <i32 0, i32 5, i32 6, i32 3>

Differential Revision: http://reviews.llvm.org/D22114

llvm-svn: 275289
This commit is contained in:
Sanjay Patel 2016-07-13 18:07:02 +00:00
parent 0532c190f7
commit c00e48a3db
2 changed files with 69 additions and 19 deletions
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43
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1589,10 +1589,29 @@ Instruction *InstCombiner::MatchBSwap(BinaryOperator &I) {
return LastInst;
}
/// If all elements of two constant vectors are 0/-1 and inverses, return true.
static bool areInverseVectorBitmasks(Constant *C1, Constant *C2) {
unsigned NumElts = C1->getType()->getVectorNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
Constant *EltC1 = C1->getAggregateElement(i);
Constant *EltC2 = C2->getAggregateElement(i);
if (!EltC1 || !EltC2)
return false;
// One element must be all ones, and the other must be all zeros.
// FIXME: Allow undef elements.
if (!((match(EltC1, m_Zero()) && match(EltC2, m_AllOnes())) ||
(match(EltC2, m_Zero()) && match(EltC1, m_AllOnes()))))
return false;
}
return true;
}
/// We have an expression of the form (A & C) | (B & D). If A is a scalar or
/// vector composed of all-zeros or all-ones values and is the bitwise 'not' of
/// B, it can be used as the condition operand of a select instruction.
static Value *getSelectCondition(Value *A, Value *B) {
static Value *getSelectCondition(Value *A, Value *B,
InstCombiner::BuilderTy &Builder) {
// If these are scalars or vectors of i1, A can be used directly.
Type *Ty = A->getType();
if (match(A, m_Not(m_Specific(B))) && Ty->getScalarType()->isIntegerTy(1))
@ -1606,8 +1625,26 @@ static Value *getSelectCondition(Value *A, Value *B) {
m_SExt(m_Not(m_Specific(Cond))))))
return Cond;
// TODO: Try more matches that only apply to non-splat constant vectors.
// All scalar (and most vector) possibilities should be handled now.
// Try more matches that only apply to non-splat constant vectors.
if (!Ty->isVectorTy())
return nullptr;
// If both operands are constants, see if the constants are inverse bitmasks.
Constant *AC, *BC;
if (match(A, m_Constant(AC)) && match(B, m_Constant(BC)) &&
areInverseVectorBitmasks(AC, BC))
return ConstantExpr::getTrunc(AC, CmpInst::makeCmpResultType(Ty));
// If both operands are xor'd with constants using the same sexted boolean
// operand, see if the constants are inverse bitmasks.
if (match(A, (m_Xor(m_SExt(m_Value(Cond)), m_Constant(AC)))) &&
match(B, (m_Xor(m_SExt(m_Specific(Cond)), m_Constant(BC)))) &&
Cond->getType()->getScalarType()->isIntegerTy(1) &&
areInverseVectorBitmasks(AC, BC)) {
AC = ConstantExpr::getTrunc(AC, CmpInst::makeCmpResultType(Ty));
return Builder.CreateXor(Cond, AC);
}
return nullptr;
}
@ -1625,7 +1662,7 @@ static Value *matchSelectFromAndOr(Value *A, Value *C, Value *B, Value *D,
B = SrcB;
}
if (Value *Cond = getSelectCondition(A, B)) {
if (Value *Cond = getSelectCondition(A, B, Builder)) {
// ((bc Cond) & C) | ((bc ~Cond) & D) --> bc (select Cond, (bc C), (bc D))
// The bitcasts will either all exist or all not exist. The builder will
// not create unnecessary casts if the types already match.

45
llvm/test/Transforms/InstCombine/logical-select.ll
View File

@ -366,15 +366,12 @@ define i4 @vec_of_casted_bools(i4 %a, i4 %b, <4 x i1> %c) {
ret i4 %or
}
; FIXME: Missed conversions to select below here.
; Inverted 'and' constants mean this is a select.
define <4 x i32> @vec_sel_consts(<4 x i32> %a, <4 x i32> %b) {
; CHECK-LABEL: @vec_sel_consts(
; CHECK-NEXT: [[AND1:%.*]] = and <4 x i32> %a, <i32 -1, i32 0, i32 0, i32 -1>
; CHECK-NEXT: [[AND2:%.*]] = and <4 x i32> %b, <i32 0, i32 -1, i32 -1, i32 0>
; CHECK-NEXT: [[OR:%.*]] = or <4 x i32> [[AND1]], [[AND2]]
; CHECK-NEXT: ret <4 x i32> [[OR]]
; CHECK-NEXT: [[TMP1:%.*]] = select <4 x i1> <i1 true, i1 false, i1 false, i1 true>, <4 x i32> %a, <4 x i32> %b
; CHECK-NEXT: ret <4 x i32> [[TMP1]]
;
%and1 = and <4 x i32> %a, <i32 -1, i32 0, i32 0, i32 -1>
%and2 = and <4 x i32> %b, <i32 0, i32 -1, i32 -1, i32 0>
@ -386,10 +383,8 @@ define <4 x i32> @vec_sel_consts(<4 x i32> %a, <4 x i32> %b) {
define <3 x i129> @vec_sel_consts_weird(<3 x i129> %a, <3 x i129> %b) {
; CHECK-LABEL: @vec_sel_consts_weird(
; CHECK-NEXT: [[AND1:%.*]] = and <3 x i129> %a, <i129 -1, i129 0, i129 -1>
; CHECK-NEXT: [[AND2:%.*]] = and <3 x i129> %b, <i129 0, i129 -1, i129 0>
; CHECK-NEXT: [[OR:%.*]] = or <3 x i129> [[AND2]], [[AND1]]
; CHECK-NEXT: ret <3 x i129> [[OR]]
; CHECK-NEXT: [[TMP1:%.*]] = select <3 x i1> <i1 false, i1 true, i1 false>, <3 x i129> %b, <3 x i129> %a
; CHECK-NEXT: ret <3 x i129> [[TMP1]]
;
%and1 = and <3 x i129> %a, <i129 -1, i129 0, i129 -1>
%and2 = and <3 x i129> %b, <i129 0, i129 -1, i129 0>
@ -416,13 +411,9 @@ define <4 x i32> @vec_not_sel_consts(<4 x i32> %a, <4 x i32> %b) {
define <4 x i32> @vec_sel_xor(<4 x i32> %a, <4 x i32> %b, <4 x i1> %c) {
; CHECK-LABEL: @vec_sel_xor(
; CHECK-NEXT: [[MASK:%.*]] = sext <4 x i1> %c to <4 x i32>
; CHECK-NEXT: [[MASK_FLIP1:%.*]] = xor <4 x i32> [[MASK]], <i32 -1, i32 0, i32 0, i32 0>
; CHECK-NEXT: [[NOT_MASK_FLIP1:%.*]] = xor <4 x i32> [[MASK]], <i32 0, i32 -1, i32 -1, i32 -1>
; CHECK-NEXT: [[AND1:%.*]] = and <4 x i32> [[NOT_MASK_FLIP1]], %a
; CHECK-NEXT: [[AND2:%.*]] = and <4 x i32> [[MASK_FLIP1]], %b
; CHECK-NEXT: [[OR:%.*]] = or <4 x i32> [[AND1]], [[AND2]]
; CHECK-NEXT: ret <4 x i32> [[OR]]
; CHECK-NEXT: [[TMP1:%.*]] = xor <4 x i1> %c, <i1 false, i1 true, i1 true, i1 true>
; CHECK-NEXT: [[TMP2:%.*]] = select <4 x i1> [[TMP1]], <4 x i32> %a, <4 x i32> %b
; CHECK-NEXT: ret <4 x i32> [[TMP2]]
;
%mask = sext <4 x i1> %c to <4 x i32>
%mask_flip1 = xor <4 x i32> %mask, <i32 -1, i32 0, i32 0, i32 0>
@ -433,3 +424,25 @@ define <4 x i32> @vec_sel_xor(<4 x i32> %a, <4 x i32> %b, <4 x i1> %c) {
ret <4 x i32> %or
}
; Allow the transform even if the mask values have multiple uses because
; there's still a net reduction of instructions from removing the and/and/or.
define <4 x i32> @vec_sel_xor_multi_use(<4 x i32> %a, <4 x i32> %b, <4 x i1> %c) {
; CHECK-LABEL: @vec_sel_xor_multi_use(
; CHECK-NEXT: [[MASK:%.*]] = sext <4 x i1> %c to <4 x i32>
; CHECK-NEXT: [[MASK_FLIP1:%.*]] = xor <4 x i32> [[MASK]], <i32 -1, i32 0, i32 0, i32 0>
; CHECK-NEXT: [[TMP1:%.*]] = xor <4 x i1> %c, <i1 false, i1 true, i1 true, i1 true>
; CHECK-NEXT: [[TMP2:%.*]] = select <4 x i1> [[TMP1]], <4 x i32> %a, <4 x i32> %b
; CHECK-NEXT: [[ADD:%.*]] = add <4 x i32> [[TMP2]], [[MASK_FLIP1]]
; CHECK-NEXT: ret <4 x i32> [[ADD]]
;
%mask = sext <4 x i1> %c to <4 x i32>
%mask_flip1 = xor <4 x i32> %mask, <i32 -1, i32 0, i32 0, i32 0>
%not_mask_flip1 = xor <4 x i32> %mask, <i32 0, i32 -1, i32 -1, i32 -1>
%and1 = and <4 x i32> %not_mask_flip1, %a
%and2 = and <4 x i32> %mask_flip1, %b
%or = or <4 x i32> %and1, %and2
%add = add <4 x i32> %or, %mask_flip1
ret <4 x i32> %add
}