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[InstCombine] add narrowing transform for low-masked binop with zext operand (2nd try)

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The 1st try ( afa192cfb6 ) was reverted because it could
cause an infinite loop with constant expressions.

A test for that and an extra condition to enable the transform
are added now. I also added code comments to better describe
the transform and the existing, related transform.

Original commit message:
https://alive2.llvm.org/ce/z/hRy3rE

As shown in D123408, we can produce this pattern when moving
casts around, and we already have a related fold for a binop
with a constant operand.
This commit is contained in:
Sanjay Patel 2022-06-10 10:44:13 -04:00
parent 4c3139d7b9
commit e247b0e5c9
3 changed files with 62 additions and 22 deletions
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34
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1855,7 +1855,7 @@ Instruction *InstCombinerImpl::visitAnd(BinaryOperator &I) {
// ((C1 OP zext(X)) & C2) -> zext((C1 OP X) & C2) if C2 fits in the
// bitwidth of X and OP behaves well when given trunc(C1) and X.
auto isSuitableBinOpcode = [](BinaryOperator *B) {
auto isNarrowableBinOpcode = [](BinaryOperator *B) {
switch (B->getOpcode()) {
case Instruction::Xor:
case Instruction::Or:
@ -1868,22 +1868,48 @@ Instruction *InstCombinerImpl::visitAnd(BinaryOperator &I) {
}
};
BinaryOperator *BO;
if (match(Op0, m_OneUse(m_BinOp(BO))) && isSuitableBinOpcode(BO)) {
if (match(Op0, m_OneUse(m_BinOp(BO))) && isNarrowableBinOpcode(BO)) {
Instruction::BinaryOps BOpcode = BO->getOpcode();
Value *X;
const APInt *C1;
// TODO: The one-use restrictions could be relaxed a little if the AND
// is going to be removed.
// Try to narrow the 'and' and a binop with constant operand:
// and (bo (zext X), C1), C --> zext (and (bo X, TruncC1), TruncC)
if (match(BO, m_c_BinOp(m_OneUse(m_ZExt(m_Value(X))), m_APInt(C1))) &&
C->isIntN(X->getType()->getScalarSizeInBits())) {
unsigned XWidth = X->getType()->getScalarSizeInBits();
Constant *TruncC1 = ConstantInt::get(X->getType(), C1->trunc(XWidth));
Value *BinOp = isa<ZExtInst>(BO->getOperand(0))
? Builder.CreateBinOp(BO->getOpcode(), X, TruncC1)
: Builder.CreateBinOp(BO->getOpcode(), TruncC1, X);
? Builder.CreateBinOp(BOpcode, X, TruncC1)
: Builder.CreateBinOp(BOpcode, TruncC1, X);
Constant *TruncC = ConstantInt::get(X->getType(), C->trunc(XWidth));
Value *And = Builder.CreateAnd(BinOp, TruncC);
return new ZExtInst(And, Ty);
}
// Similar to above: if the mask matches the zext input width, then the
// 'and' can be eliminated, so we can truncate the other variable op:
// and (bo (zext X), Y), C --> zext (bo X, (trunc Y))
if (isa<Instruction>(BO->getOperand(0)) &&
match(BO->getOperand(0), m_OneUse(m_ZExt(m_Value(X)))) &&
C->isMask(X->getType()->getScalarSizeInBits())) {
Y = BO->getOperand(1);
Value *TrY = Builder.CreateTrunc(Y, X->getType(), Y->getName() + ".tr");
Value *NewBO =
Builder.CreateBinOp(BOpcode, X, TrY, BO->getName() + ".narrow");
return new ZExtInst(NewBO, Ty);
}
// and (bo Y, (zext X)), C --> zext (bo (trunc Y), X)
if (isa<Instruction>(BO->getOperand(1)) &&
match(BO->getOperand(1), m_OneUse(m_ZExt(m_Value(X)))) &&
C->isMask(X->getType()->getScalarSizeInBits())) {
Y = BO->getOperand(0);
Value *TrY = Builder.CreateTrunc(Y, X->getType(), Y->getName() + ".tr");
Value *NewBO =
Builder.CreateBinOp(BOpcode, TrY, X, BO->getName() + ".narrow");
return new ZExtInst(NewBO, Ty);
}
}
Constant *C1, *C2;

44
llvm/test/Transforms/InstCombine/and.ll
View File

@ -744,9 +744,9 @@ define i64 @test39(i32 %X) {
define i32 @lowmask_add_zext(i8 %x, i32 %y) {
; CHECK-LABEL: @lowmask_add_zext(
; CHECK-NEXT: [[ZX:%.*]] = zext i8 [[X:%.*]] to i32
; CHECK-NEXT: [[BO:%.*]] = add i32 [[ZX]], [[Y:%.*]]
; CHECK-NEXT: [[R:%.*]] = and i32 [[BO]], 255
; CHECK-NEXT: [[Y_TR:%.*]] = trunc i32 [[Y:%.*]] to i8
; CHECK-NEXT: [[BO_NARROW:%.*]] = add i8 [[Y_TR]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = zext i8 [[BO_NARROW]] to i32
; CHECK-NEXT: ret i32 [[R]]
;
%zx = zext i8 %x to i32
@ -758,9 +758,9 @@ define i32 @lowmask_add_zext(i8 %x, i32 %y) {
define i32 @lowmask_add_zext_commute(i16 %x, i32 %p) {
; CHECK-LABEL: @lowmask_add_zext_commute(
; CHECK-NEXT: [[Y:%.*]] = mul i32 [[P:%.*]], [[P]]
; CHECK-NEXT: [[ZX:%.*]] = zext i16 [[X:%.*]] to i32
; CHECK-NEXT: [[BO:%.*]] = add i32 [[Y]], [[ZX]]
; CHECK-NEXT: [[R:%.*]] = and i32 [[BO]], 65535
; CHECK-NEXT: [[Y_TR:%.*]] = trunc i32 [[Y]] to i16
; CHECK-NEXT: [[BO_NARROW:%.*]] = add i16 [[Y_TR]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = zext i16 [[BO_NARROW]] to i32
; CHECK-NEXT: ret i32 [[R]]
;
%y = mul i32 %p, %p ; thwart complexity-based canonicalization
@ -770,6 +770,8 @@ define i32 @lowmask_add_zext_commute(i16 %x, i32 %p) {
ret i32 %r
}
; negative test - the mask constant must match the zext source type
define i32 @lowmask_add_zext_wrong_mask(i8 %x, i32 %y) {
; CHECK-LABEL: @lowmask_add_zext_wrong_mask(
; CHECK-NEXT: [[ZX:%.*]] = zext i8 [[X:%.*]] to i32
@ -783,6 +785,8 @@ define i32 @lowmask_add_zext_wrong_mask(i8 %x, i32 %y) {
ret i32 %r
}
; negative test - extra use
define i32 @lowmask_add_zext_use1(i8 %x, i32 %y) {
; CHECK-LABEL: @lowmask_add_zext_use1(
; CHECK-NEXT: [[ZX:%.*]] = zext i8 [[X:%.*]] to i32
@ -798,6 +802,8 @@ define i32 @lowmask_add_zext_use1(i8 %x, i32 %y) {
ret i32 %r
}
; negative test - extra use
define i32 @lowmask_add_zext_use2(i8 %x, i32 %y) {
; CHECK-LABEL: @lowmask_add_zext_use2(
; CHECK-NEXT: [[ZX:%.*]] = zext i8 [[X:%.*]] to i32
@ -813,11 +819,13 @@ define i32 @lowmask_add_zext_use2(i8 %x, i32 %y) {
ret i32 %r
}
; vector splats work too
define <2 x i32> @lowmask_sub_zext(<2 x i4> %x, <2 x i32> %y) {
; CHECK-LABEL: @lowmask_sub_zext(
; CHECK-NEXT: [[ZX:%.*]] = zext <2 x i4> [[X:%.*]] to <2 x i32>
; CHECK-NEXT: [[BO:%.*]] = sub <2 x i32> [[ZX]], [[Y:%.*]]
; CHECK-NEXT: [[R:%.*]] = and <2 x i32> [[BO]], <i32 15, i32 15>
; CHECK-NEXT: [[Y_TR:%.*]] = trunc <2 x i32> [[Y:%.*]] to <2 x i4>
; CHECK-NEXT: [[BO_NARROW:%.*]] = sub <2 x i4> [[X:%.*]], [[Y_TR]]
; CHECK-NEXT: [[R:%.*]] = zext <2 x i4> [[BO_NARROW]] to <2 x i32>
; CHECK-NEXT: ret <2 x i32> [[R]]
;
%zx = zext <2 x i4> %x to <2 x i32>
@ -826,11 +834,13 @@ define <2 x i32> @lowmask_sub_zext(<2 x i4> %x, <2 x i32> %y) {
ret <2 x i32> %r
}
; weird types are allowed
define i17 @lowmask_sub_zext_commute(i5 %x, i17 %y) {
; CHECK-LABEL: @lowmask_sub_zext_commute(
; CHECK-NEXT: [[ZX:%.*]] = zext i5 [[X:%.*]] to i17
; CHECK-NEXT: [[BO:%.*]] = sub i17 [[Y:%.*]], [[ZX]]
; CHECK-NEXT: [[R:%.*]] = and i17 [[BO]], 31
; CHECK-NEXT: [[Y_TR:%.*]] = trunc i17 [[Y:%.*]] to i5
; CHECK-NEXT: [[BO_NARROW:%.*]] = sub i5 [[Y_TR]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = zext i5 [[BO_NARROW]] to i17
; CHECK-NEXT: ret i17 [[R]]
;
%zx = zext i5 %x to i17
@ -841,9 +851,9 @@ define i17 @lowmask_sub_zext_commute(i5 %x, i17 %y) {
define i32 @lowmask_mul_zext(i8 %x, i32 %y) {
; CHECK-LABEL: @lowmask_mul_zext(
; CHECK-NEXT: [[ZX:%.*]] = zext i8 [[X:%.*]] to i32
; CHECK-NEXT: [[BO:%.*]] = mul i32 [[ZX]], [[Y:%.*]]
; CHECK-NEXT: [[R:%.*]] = and i32 [[BO]], 255
; CHECK-NEXT: [[Y_TR:%.*]] = trunc i32 [[Y:%.*]] to i8
; CHECK-NEXT: [[BO_NARROW:%.*]] = mul i8 [[Y_TR]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = zext i8 [[BO_NARROW]] to i32
; CHECK-NEXT: ret i32 [[R]]
;
%zx = zext i8 %x to i32
@ -852,6 +862,8 @@ define i32 @lowmask_mul_zext(i8 %x, i32 %y) {
ret i32 %r
}
; TODO: we could have narrowed the xor
define i32 @lowmask_xor_zext_commute(i8 %x, i32 %p) {
; CHECK-LABEL: @lowmask_xor_zext_commute(
; CHECK-NEXT: [[Y:%.*]] = mul i32 [[P:%.*]], [[P]]
@ -867,6 +879,8 @@ define i32 @lowmask_xor_zext_commute(i8 %x, i32 %p) {
ret i32 %r
}
; TODO: we could have narrowed the or
define i24 @lowmask_or_zext_commute(i16 %x, i24 %y) {
; CHECK-LABEL: @lowmask_or_zext_commute(
; CHECK-NEXT: [[ZX:%.*]] = zext i16 [[X:%.*]] to i24

6
llvm/test/Transforms/InstCombine/cast_phi.ll
View File

@ -357,9 +357,9 @@ define i32 @zext_in_loop_and_exit_block(i8 %step, i32 %end) {
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp eq i32 [[IV]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[EXIT:%.*]], label [[LOOP_LATCH]]
; CHECK: loop.latch:
; CHECK-NEXT: [[STEP_EXT:%.*]] = zext i8 [[STEP:%.*]] to i32
; CHECK-NEXT: [[IV_NEXT:%.*]] = add nuw nsw i32 [[IV]], [[STEP_EXT]]
; CHECK-NEXT: [[PHI_CAST]] = and i32 [[IV_NEXT]], 255
; CHECK-NEXT: [[IV_TR:%.*]] = trunc i32 [[IV]] to i8
; CHECK-NEXT: [[IV_NEXT_NARROW:%.*]] = add i8 [[IV_TR]], [[STEP:%.*]]
; CHECK-NEXT: [[PHI_CAST]] = zext i8 [[IV_NEXT_NARROW]] to i32
; CHECK-NEXT: br label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: ret i32 [[IV]]