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[AArch64][SVE] Fix missed immediate selection due to mishandling of signedness 

The complex selection pattern for add/sub shifted immediates is
incorrect in it's handling of incoming constant values, in that it
does not properly anticipate the values to be signed extended to
32-bits.

Co-authored-by: Graham Hunter <graham.hunter@arm.com>

Differential Revision: https://reviews.llvm.org/D101833
This commit is contained in:
Bradley Smith 2021-05-04 11:18:34 +01:00
parent cf194da1bb
commit b1a074951f
2 changed files with 34 additions and 2 deletions
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16
llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
View File

@ -3100,20 +3100,32 @@ bool AArch64DAGToDAGISel::SelectSVE8BitLslImm(SDValue N, SDValue &Base,
bool AArch64DAGToDAGISel::SelectSVEAddSubImm(SDValue N, MVT VT, SDValue &Imm, SDValue &Shift) {
if (auto CNode = dyn_cast<ConstantSDNode>(N)) {
const int64_t ImmVal = CNode->getZExtValue();
const int64_t ImmVal = CNode->getSExtValue();
SDLoc DL(N);
switch (VT.SimpleTy) {
case MVT::i8:
// Can always select i8s, no shift, mask the immediate value to
// deal with sign-extended value from lowering.
Shift = CurDAG->getTargetConstant(0, DL, MVT::i32);
Imm = CurDAG->getTargetConstant(ImmVal & 0xFF, DL, MVT::i32);
return true;
case MVT::i16:
// i16 values get sign-extended to 32-bits during lowering.
if ((ImmVal & 0xFF) == ImmVal) {
Shift = CurDAG->getTargetConstant(0, DL, MVT::i32);
Imm = CurDAG->getTargetConstant(ImmVal, DL, MVT::i32);
return true;
} else if ((ImmVal & 0xFF) == 0) {
assert((ImmVal >= -32768) && (ImmVal <= 32512));
Shift = CurDAG->getTargetConstant(8, DL, MVT::i32);
Imm = CurDAG->getTargetConstant((ImmVal >> 8) & 0xFF, DL, MVT::i32);
return true;
}
break;
case MVT::i16:
case MVT::i32:
case MVT::i64:
// Range of immediate won't trigger signedness problems for 32/64b.
if ((ImmVal & 0xFF) == ImmVal) {
Shift = CurDAG->getTargetConstant(0, DL, MVT::i32);
Imm = CurDAG->getTargetConstant(ImmVal, DL, MVT::i32);

20
llvm/test/CodeGen/AArch64/sve-int-imm.ll
View File

@ -75,6 +75,26 @@ define <vscale x 2 x i64> @add_i64_high(<vscale x 2 x i64> %a) {
ret <vscale x 2 x i64> %res
}
define <vscale x 16 x i8> @add_i8_signedness(<vscale x 16 x i8> %a) {
; CHECK-LABEL: add_i8_signedness
; CHECK: add z0.b, z0.b, #255
; CHECK-NEXT: ret
%elt = insertelement <vscale x 16 x i8> undef, i8 255, i32 0
%splat = shufflevector <vscale x 16 x i8> %elt, <vscale x 16 x i8> undef, <vscale x 16 x i32> zeroinitializer
%res = add <vscale x 16 x i8> %a, %splat
ret <vscale x 16 x i8> %res
}
define <vscale x 8 x i16> @add_i16_signedness(<vscale x 8 x i16> %a) {
; CHECK-LABEL: add_i16_signedness
; CHECK: add z0.h, z0.h, #65280
; CHECK-NEXT: ret
%elt = insertelement <vscale x 8 x i16> undef, i16 65280, i32 0
%splat = shufflevector <vscale x 8 x i16> %elt, <vscale x 8 x i16> undef, <vscale x 8 x i32> zeroinitializer
%res = add <vscale x 8 x i16> %a, %splat
ret <vscale x 8 x i16> %res
}
; SUBR
define <vscale x 16 x i8> @subr_i8_low(<vscale x 16 x i8> %a) {
; CHECK-LABEL: subr_i8_low