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[DAG] Fold trunc(abdu(x,y)) and trunc(abds(x,y)) if they have sufficient leading zero/sign bits (#151471)
This PR resolves llvm/llvm-project#147683 --------- Co-authored-by: Simon Pilgrim <[email protected]>
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-29
lines changed

3 files changed

+114
-29
lines changed

‎llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp‎

Lines changed: 32 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -16342,6 +16342,38 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
1634216342
DAG, DL);
1634316343
}
1634416344
break;
16345+
case ISD::ABDU:
16346+
case ISD::ABDS:
16347+
// (trunc (abdu/abds a, b)) → (abdu/abds (trunc a), (trunc b))
16348+
if (!LegalOperations || N0.hasOneUse()) {
16349+
EVT SrcVT = N0.getValueType();
16350+
EVT TruncVT = VT;
16351+
unsigned SrcBits = SrcVT.getScalarSizeInBits();
16352+
unsigned TruncBits = TruncVT.getScalarSizeInBits();
16353+
unsigned NeededBits = SrcBits - TruncBits;
16354+
16355+
SDValue A = N0.getOperand(0);
16356+
SDValue B = N0.getOperand(1);
16357+
bool CanFold = false;
16358+
16359+
if (N0.getOpcode() == ISD::ABDU) {
16360+
KnownBits KnownA = DAG.computeKnownBits(A);
16361+
KnownBits KnownB = DAG.computeKnownBits(B);
16362+
CanFold = KnownA.countMinLeadingZeros() >= NeededBits &&
16363+
KnownB.countMinLeadingZeros() >= NeededBits;
16364+
} else {
16365+
unsigned SignBitsA = DAG.ComputeNumSignBits(A);
16366+
unsigned SignBitsB = DAG.ComputeNumSignBits(B);
16367+
CanFold = SignBitsA > NeededBits && SignBitsB > NeededBits;
16368+
}
16369+
16370+
if (CanFold && TLI.isOperationLegal(N0.getOpcode(), VT)) {
16371+
SDValue NewA = DAG.getNode(ISD::TRUNCATE, DL, TruncVT, A);
16372+
SDValue NewB = DAG.getNode(ISD::TRUNCATE, DL, TruncVT, B);
16373+
return DAG.getNode(N0.getOpcode(), DL, TruncVT, NewA, NewB);
16374+
}
16375+
}
16376+
break;
1634516377
}
1634616378

1634716379
return SDValue();

‎llvm/test/CodeGen/AArch64/abd-combine.ll‎

Lines changed: 16 additions & 29 deletions
Original file line numberDiff line numberDiff line change
@@ -17,12 +17,9 @@ define <8 x i16> @abdu_base(<8 x i16> %src1, <8 x i16> %src2) {
1717
define <8 x i16> @abdu_const(<8 x i16> %src1) {
1818
; CHECK-LABEL: abdu_const:
1919
; CHECK: // %bb.0:
20-
; CHECK-NEXT: movi v1.4s, #1
21-
; CHECK-NEXT: ushll v2.4s, v0.4h, #0
22-
; CHECK-NEXT: ushll2 v0.4s, v0.8h, #0
23-
; CHECK-NEXT: uabd v0.4s, v0.4s, v1.4s
24-
; CHECK-NEXT: uabd v1.4s, v2.4s, v1.4s
25-
; CHECK-NEXT: uzp1 v0.8h, v1.8h, v0.8h
20+
; CHECK-NEXT: movi v1.4h, #1
21+
; CHECK-NEXT: mov v1.d[1], v1.d[0]
22+
; CHECK-NEXT: uabd v0.8h, v0.8h, v1.8h
2623
; CHECK-NEXT: ret
2724
%zextsrc1 = zext <8 x i16> %src1 to <8 x i32>
2825
%sub = sub <8 x i32> %zextsrc1, <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
@@ -34,12 +31,9 @@ define <8 x i16> @abdu_const(<8 x i16> %src1) {
3431
define <8 x i16> @abdu_const_lhs(<8 x i16> %src1) {
3532
; CHECK-LABEL: abdu_const_lhs:
3633
; CHECK: // %bb.0:
37-
; CHECK-NEXT: movi v1.4s, #1
38-
; CHECK-NEXT: ushll v2.4s, v0.4h, #0
39-
; CHECK-NEXT: ushll2 v0.4s, v0.8h, #0
40-
; CHECK-NEXT: uabd v0.4s, v0.4s, v1.4s
41-
; CHECK-NEXT: uabd v1.4s, v2.4s, v1.4s
42-
; CHECK-NEXT: uzp1 v0.8h, v1.8h, v0.8h
34+
; CHECK-NEXT: movi v1.4h, #1
35+
; CHECK-NEXT: mov v1.d[1], v1.d[0]
36+
; CHECK-NEXT: uabd v0.8h, v0.8h, v1.8h
4337
; CHECK-NEXT: ret
4438
%zextsrc1 = zext <8 x i16> %src1 to <8 x i32>
4539
%sub = sub <8 x i32> <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>, %zextsrc1
@@ -318,12 +312,9 @@ define <8 x i16> @abds_base(<8 x i16> %src1, <8 x i16> %src2) {
318312
define <8 x i16> @abds_const(<8 x i16> %src1) {
319313
; CHECK-LABEL: abds_const:
320314
; CHECK: // %bb.0:
321-
; CHECK-NEXT: movi v1.4s, #1
322-
; CHECK-NEXT: sshll v2.4s, v0.4h, #0
323-
; CHECK-NEXT: sshll2 v0.4s, v0.8h, #0
324-
; CHECK-NEXT: sabd v0.4s, v0.4s, v1.4s
325-
; CHECK-NEXT: sabd v1.4s, v2.4s, v1.4s
326-
; CHECK-NEXT: uzp1 v0.8h, v1.8h, v0.8h
315+
; CHECK-NEXT: movi v1.4h, #1
316+
; CHECK-NEXT: mov v1.d[1], v1.d[0]
317+
; CHECK-NEXT: sabd v0.8h, v0.8h, v1.8h
327318
; CHECK-NEXT: ret
328319
%zextsrc1 = sext <8 x i16> %src1 to <8 x i32>
329320
%sub = sub <8 x i32> %zextsrc1, <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
@@ -335,12 +326,9 @@ define <8 x i16> @abds_const(<8 x i16> %src1) {
335326
define <8 x i16> @abds_const_lhs(<8 x i16> %src1) {
336327
; CHECK-LABEL: abds_const_lhs:
337328
; CHECK: // %bb.0:
338-
; CHECK-NEXT: movi v1.4s, #1
339-
; CHECK-NEXT: sshll v2.4s, v0.4h, #0
340-
; CHECK-NEXT: sshll2 v0.4s, v0.8h, #0
341-
; CHECK-NEXT: sabd v0.4s, v0.4s, v1.4s
342-
; CHECK-NEXT: sabd v1.4s, v2.4s, v1.4s
343-
; CHECK-NEXT: uzp1 v0.8h, v1.8h, v0.8h
329+
; CHECK-NEXT: movi v1.4h, #1
330+
; CHECK-NEXT: mov v1.d[1], v1.d[0]
331+
; CHECK-NEXT: sabd v0.8h, v0.8h, v1.8h
344332
; CHECK-NEXT: ret
345333
%zextsrc1 = sext <8 x i16> %src1 to <8 x i32>
346334
%sub = sub <8 x i32> <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>, %zextsrc1
@@ -352,11 +340,10 @@ define <8 x i16> @abds_const_lhs(<8 x i16> %src1) {
352340
define <8 x i16> @abds_const_zero(<8 x i16> %src1) {
353341
; CHECK-LABEL: abds_const_zero:
354342
; CHECK: // %bb.0:
355-
; CHECK-NEXT: sshll v1.4s, v0.4h, #0
356-
; CHECK-NEXT: sshll2 v0.4s, v0.8h, #0
357-
; CHECK-NEXT: abs v0.4s, v0.4s
358-
; CHECK-NEXT: abs v1.4s, v1.4s
359-
; CHECK-NEXT: uzp1 v0.8h, v1.8h, v0.8h
343+
; CHECK-NEXT: ext v1.16b, v0.16b, v0.16b, #8
344+
; CHECK-NEXT: abs v0.4h, v0.4h
345+
; CHECK-NEXT: abs v1.4h, v1.4h
346+
; CHECK-NEXT: mov v0.d[1], v1.d[0]
360347
; CHECK-NEXT: ret
361348
%zextsrc1 = sext <8 x i16> %src1 to <8 x i32>
362349
%sub = sub <8 x i32> <i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0>, %zextsrc1

‎llvm/test/CodeGen/AArch64/arm64-neon-aba-abd.ll‎

Lines changed: 66 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -575,3 +575,69 @@ define <4 x i32> @knownbits_sabd_and_mul_mask(<4 x i32> %a0, <4 x i32> %a1) {
575575
%6 = shufflevector <4 x i32> %5, <4 x i32> undef, <4 x i32> <i32 0, i32 0, i32 3, i32 3>
576576
ret <4 x i32> %6
577577
}
578+
579+
define <4 x i16> @trunc_abdu_foldable(<4 x i16> %a, <4 x i16> %b) {
580+
; CHECK-SD-LABEL: trunc_abdu_foldable:
581+
; CHECK-SD: // %bb.0:
582+
; CHECK-SD-NEXT: uabd v0.4h, v0.4h, v1.4h
583+
; CHECK-SD-NEXT: ret
584+
;
585+
; CHECK-GI-LABEL: trunc_abdu_foldable:
586+
; CHECK-GI: // %bb.0:
587+
; CHECK-GI-NEXT: ushll v0.4s, v0.4h, #0
588+
; CHECK-GI-NEXT: ushll v1.4s, v1.4h, #0
589+
; CHECK-GI-NEXT: uabd v0.4s, v0.4s, v1.4s
590+
; CHECK-GI-NEXT: xtn v0.4h, v0.4s
591+
; CHECK-GI-NEXT: ret
592+
%ext_a = zext <4 x i16> %a to <4 x i32>
593+
%ext_b = zext <4 x i16> %b to <4 x i32>
594+
%abd = call <4 x i32> @llvm.aarch64.neon.uabd.v4i32(<4 x i32> %ext_a, <4 x i32> %ext_b)
595+
%trunc = trunc <4 x i32> %abd to <4 x i16>
596+
ret <4 x i16> %trunc
597+
}
598+
599+
define <4 x i16> @trunc_abds_foldable(<4 x i16> %a, <4 x i16> %b) {
600+
; CHECK-SD-LABEL: trunc_abds_foldable:
601+
; CHECK-SD: // %bb.0:
602+
; CHECK-SD-NEXT: sabd v0.4h, v0.4h, v1.4h
603+
; CHECK-SD-NEXT: ret
604+
;
605+
; CHECK-GI-LABEL: trunc_abds_foldable:
606+
; CHECK-GI: // %bb.0:
607+
; CHECK-GI-NEXT: sshll v0.4s, v0.4h, #0
608+
; CHECK-GI-NEXT: sshll v1.4s, v1.4h, #0
609+
; CHECK-GI-NEXT: sabd v0.4s, v0.4s, v1.4s
610+
; CHECK-GI-NEXT: xtn v0.4h, v0.4s
611+
; CHECK-GI-NEXT: ret
612+
%a32 = sext <4 x i16> %a to <4 x i32>
613+
%b32 = sext <4 x i16> %b to <4 x i32>
614+
%abd32 = call <4 x i32> @llvm.aarch64.neon.sabd.v4i32(<4 x i32> %a32, <4 x i32> %b32)
615+
%res16 = trunc <4 x i32> %abd32 to <4 x i16>
616+
ret <4 x i16> %res16
617+
}
618+
619+
define <4 x i16> @trunc_abdu_not_foldable(<4 x i16> %a, <4 x i32> %b) {
620+
; CHECK-LABEL: trunc_abdu_not_foldable:
621+
; CHECK: // %bb.0:
622+
; CHECK-NEXT: ushll v0.4s, v0.4h, #0
623+
; CHECK-NEXT: uabd v0.4s, v0.4s, v1.4s
624+
; CHECK-NEXT: xtn v0.4h, v0.4s
625+
; CHECK-NEXT: ret
626+
%ext_a = zext <4 x i16> %a to <4 x i32>
627+
%abd = call <4 x i32> @llvm.aarch64.neon.uabd.v4i32(<4 x i32> %ext_a, <4 x i32> %b)
628+
%trunc = trunc <4 x i32> %abd to <4 x i16>
629+
ret <4 x i16> %trunc
630+
}
631+
632+
define <4 x i16> @truncate_abds_testcase1(<4 x i16> %a, <4 x i32> %b) {
633+
; CHECK-LABEL: truncate_abds_testcase1:
634+
; CHECK: // %bb.0:
635+
; CHECK-NEXT: sshll v0.4s, v0.4h, #0
636+
; CHECK-NEXT: sabd v0.4s, v0.4s, v1.4s
637+
; CHECK-NEXT: xtn v0.4h, v0.4s
638+
; CHECK-NEXT: ret
639+
%a32 = sext <4 x i16> %a to <4 x i32>
640+
%abd32 = call <4 x i32> @llvm.aarch64.neon.sabd.v4i32(<4 x i32> %a32, <4 x i32> %b)
641+
%res16 = trunc <4 x i32> %abd32 to <4 x i16>
642+
ret <4 x i16> %res16
643+
}

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