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[DAG] isBitwiseNot / isConstOrConstSplat - add support for build vector undefs + truncation (PR41020) 

Add (opt-in) support for implicit truncation to isConstOrConstSplat, which allows us to match truncated 'all ones' cases in isBitwiseNot.

PR41020 compares against using ISD::isBuildVectorAllOnes() instead, but that predicate silently accepts any UNDEF elements in the build vector which might not be what we want in isBitwiseNot - so I've added an opt-in 'AllowUndefs' flag that is set to false by default but will allow us to enable it on individual cases where its safe.

Differential Revision: https://reviews.llvm.org/D62783

llvm-svn: 362323
This commit is contained in:
Simon Pilgrim 2019-06-02 11:56:39 +00:00
parent 88522ce388
commit ffb4d2bff7
3 changed files with 41 additions and 32 deletions
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8
llvm/include/llvm/CodeGen/SelectionDAGNodes.h
View File

@ -1649,15 +1649,17 @@ SDValue peekThroughExtractSubvectors(SDValue V);
/// Returns true if \p V is a bitwise not operation. Assumes that an all ones
/// constant is canonicalized to be operand 1.
bool isBitwiseNot(SDValue V);
bool isBitwiseNot(SDValue V, bool AllowUndefs = false);
/// Returns the SDNode if it is a constant splat BuildVector or constant int.
ConstantSDNode *isConstOrConstSplat(SDValue N, bool AllowUndefs = false);
ConstantSDNode *isConstOrConstSplat(SDValue N, bool AllowUndefs = false,
bool AllowTruncation = false);
/// Returns the SDNode if it is a demanded constant splat BuildVector or
/// constant int.
ConstantSDNode *isConstOrConstSplat(SDValue N, const APInt &DemandedElts,
bool AllowUndefs = false);
bool AllowUndefs = false,
bool AllowTruncation = false);
/// Returns the SDNode if it is a constant splat BuildVector or constant float.
ConstantFPSDNode *isConstOrConstSplatFP(SDValue N, bool AllowUndefs = false);

41
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -8640,14 +8640,18 @@ SDValue llvm::peekThroughExtractSubvectors(SDValue V) {
return V;
}
bool llvm::isBitwiseNot(SDValue V) {
bool llvm::isBitwiseNot(SDValue V, bool AllowUndefs) {
if (V.getOpcode() != ISD::XOR)
return false;
ConstantSDNode *C = isConstOrConstSplat(peekThroughBitcasts(V.getOperand(1)));
return C && C->isAllOnesValue();
V = peekThroughBitcasts(V.getOperand(1));
unsigned NumBits = V.getScalarValueSizeInBits();
ConstantSDNode *C =
isConstOrConstSplat(V, AllowUndefs, /*AllowTruncation*/ true);
return C && (C->getAPIntValue().countTrailingOnes() >= NumBits);
}
ConstantSDNode *llvm::isConstOrConstSplat(SDValue N, bool AllowUndefs) {
ConstantSDNode *llvm::isConstOrConstSplat(SDValue N, bool AllowUndefs,
bool AllowTruncation) {
if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N))
return CN;
@ -8655,17 +8659,23 @@ ConstantSDNode *llvm::isConstOrConstSplat(SDValue N, bool AllowUndefs) {
BitVector UndefElements;
ConstantSDNode *CN = BV->getConstantSplatNode(&UndefElements);
// BuildVectors can truncate their operands. Ignore that case here.
if (CN && (UndefElements.none() || AllowUndefs) &&
CN->getValueType(0) == N.getValueType().getScalarType())
return CN;
// BuildVectors can truncate their operands. Ignore that case here unless
// AllowTruncation is set.
if (CN && (UndefElements.none() || AllowUndefs)) {
EVT CVT = CN->getValueType(0);
EVT NSVT = N.getValueType().getScalarType();
assert(CVT.bitsGE(NSVT) && "Illegal build vector element extension");
if (AllowTruncation || (CVT == NSVT))
return CN;
}
}
return nullptr;
}
ConstantSDNode *llvm::isConstOrConstSplat(SDValue N, const APInt &DemandedElts,
bool AllowUndefs) {
bool AllowUndefs,
bool AllowTruncation) {
if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(N))
return CN;
@ -8673,10 +8683,15 @@ ConstantSDNode *llvm::isConstOrConstSplat(SDValue N, const APInt &DemandedElts,
BitVector UndefElements;
ConstantSDNode *CN = BV->getConstantSplatNode(DemandedElts, &UndefElements);
// BuildVectors can truncate their operands. Ignore that case here.
if (CN && (UndefElements.none() || AllowUndefs) &&
CN->getValueType(0) == N.getValueType().getScalarType())
return CN;
// BuildVectors can truncate their operands. Ignore that case here unless
// AllowTruncation is set.
if (CN && (UndefElements.none() || AllowUndefs)) {
EVT CVT = CN->getValueType(0);
EVT NSVT = N.getValueType().getScalarType();
assert(CVT.bitsGE(NSVT) && "Illegal build vector element extension");
if (AllowTruncation || (CVT == NSVT))
return CN;
}
}
return nullptr;

24
llvm/test/CodeGen/AArch64/sat-add.ll
View File

@ -364,8 +364,7 @@ define <16 x i8> @unsigned_sat_constant_v16i8_using_cmp_sum(<16 x i8> %x) {
; CHECK-NEXT: movi v1.16b, #42
; CHECK-NEXT: add v1.16b, v0.16b, v1.16b
; CHECK-NEXT: cmhi v0.16b, v0.16b, v1.16b
; CHECK-NEXT: bic v1.16b, v1.16b, v0.16b
; CHECK-NEXT: orr v0.16b, v0.16b, v1.16b
; CHECK-NEXT: orr v0.16b, v1.16b, v0.16b
; CHECK-NEXT: ret
%a = add <16 x i8> %x, <i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42>
%c = icmp ugt <16 x i8> %x, %a
@ -380,8 +379,7 @@ define <16 x i8> @unsigned_sat_constant_v16i8_using_cmp_notval(<16 x i8> %x) {
; CHECK-NEXT: movi v2.16b, #213
; CHECK-NEXT: add v1.16b, v0.16b, v1.16b
; CHECK-NEXT: cmhi v0.16b, v0.16b, v2.16b
; CHECK-NEXT: bic v1.16b, v1.16b, v0.16b
; CHECK-NEXT: orr v0.16b, v0.16b, v1.16b
; CHECK-NEXT: orr v0.16b, v1.16b, v0.16b
; CHECK-NEXT: ret
%a = add <16 x i8> %x, <i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42, i8 42>
%c = icmp ugt <16 x i8> %x, <i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43, i8 -43>
@ -409,8 +407,7 @@ define <8 x i16> @unsigned_sat_constant_v8i16_using_cmp_sum(<8 x i16> %x) {
; CHECK-NEXT: movi v1.8h, #42
; CHECK-NEXT: add v1.8h, v0.8h, v1.8h
; CHECK-NEXT: cmhi v0.8h, v0.8h, v1.8h
; CHECK-NEXT: bic v1.16b, v1.16b, v0.16b
; CHECK-NEXT: orr v0.16b, v0.16b, v1.16b
; CHECK-NEXT: orr v0.16b, v1.16b, v0.16b
; CHECK-NEXT: ret
%a = add <8 x i16> %x, <i16 42, i16 42, i16 42, i16 42, i16 42, i16 42, i16 42, i16 42>
%c = icmp ugt <8 x i16> %x, %a
@ -425,8 +422,7 @@ define <8 x i16> @unsigned_sat_constant_v8i16_using_cmp_notval(<8 x i16> %x) {
; CHECK-NEXT: mvni v2.8h, #42
; CHECK-NEXT: add v1.8h, v0.8h, v1.8h
; CHECK-NEXT: cmhi v0.8h, v0.8h, v2.8h
; CHECK-NEXT: bic v1.16b, v1.16b, v0.16b
; CHECK-NEXT: orr v0.16b, v0.16b, v1.16b
; CHECK-NEXT: orr v0.16b, v1.16b, v0.16b
; CHECK-NEXT: ret
%a = add <8 x i16> %x, <i16 42, i16 42, i16 42, i16 42, i16 42, i16 42, i16 42, i16 42>
%c = icmp ugt <8 x i16> %x, <i16 -43, i16 -43, i16 -43, i16 -43, i16 -43, i16 -43, i16 -43, i16 -43>
@ -545,8 +541,7 @@ define <16 x i8> @unsigned_sat_variable_v16i8_using_cmp_sum(<16 x i8> %x, <16 x
; CHECK: // %bb.0:
; CHECK-NEXT: add v1.16b, v0.16b, v1.16b
; CHECK-NEXT: cmhi v0.16b, v0.16b, v1.16b
; CHECK-NEXT: bic v1.16b, v1.16b, v0.16b
; CHECK-NEXT: orr v0.16b, v0.16b, v1.16b
; CHECK-NEXT: orr v0.16b, v1.16b, v0.16b
; CHECK-NEXT: ret
%a = add <16 x i8> %x, %y
%c = icmp ugt <16 x i8> %x, %a
@ -560,8 +555,7 @@ define <16 x i8> @unsigned_sat_variable_v16i8_using_cmp_notval(<16 x i8> %x, <16
; CHECK-NEXT: mvn v2.16b, v1.16b
; CHECK-NEXT: add v1.16b, v0.16b, v1.16b
; CHECK-NEXT: cmhi v0.16b, v0.16b, v2.16b
; CHECK-NEXT: bic v1.16b, v1.16b, v0.16b
; CHECK-NEXT: orr v0.16b, v0.16b, v1.16b
; CHECK-NEXT: orr v0.16b, v1.16b, v0.16b
; CHECK-NEXT: ret
%noty = xor <16 x i8> %y, <i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1>
%a = add <16 x i8> %x, %y
@ -589,8 +583,7 @@ define <8 x i16> @unsigned_sat_variable_v8i16_using_cmp_sum(<8 x i16> %x, <8 x i
; CHECK: // %bb.0:
; CHECK-NEXT: add v1.8h, v0.8h, v1.8h
; CHECK-NEXT: cmhi v0.8h, v0.8h, v1.8h
; CHECK-NEXT: bic v1.16b, v1.16b, v0.16b
; CHECK-NEXT: orr v0.16b, v0.16b, v1.16b
; CHECK-NEXT: orr v0.16b, v1.16b, v0.16b
; CHECK-NEXT: ret
%a = add <8 x i16> %x, %y
%c = icmp ugt <8 x i16> %x, %a
@ -604,8 +597,7 @@ define <8 x i16> @unsigned_sat_variable_v8i16_using_cmp_notval(<8 x i16> %x, <8
; CHECK-NEXT: mvn v2.16b, v1.16b
; CHECK-NEXT: add v1.8h, v0.8h, v1.8h
; CHECK-NEXT: cmhi v0.8h, v0.8h, v2.8h
; CHECK-NEXT: bic v1.16b, v1.16b, v0.16b
; CHECK-NEXT: orr v0.16b, v0.16b, v1.16b
; CHECK-NEXT: orr v0.16b, v1.16b, v0.16b
; CHECK-NEXT: ret
%noty = xor <8 x i16> %y, <i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1>
%a = add <8 x i16> %x, %y