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author | Nikita Popov <npopov@redhat.com> | 2024-02-13 09:29:56 +0100 |
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committer | GitHub <noreply@github.com> | 2024-02-13 09:29:56 +0100 |
commit | 070848c17c2944afa494d42d3ad42929f3379842 (patch) | |
tree | 64cdda266b0a57bcb2303c434e253d727c204f99 /llvm/lib | |
parent | 0e16950e741aee7ffec865c81596e1411471475e (diff) | |
download | llvm-070848c17c2944afa494d42d3ad42929f3379842.zip llvm-070848c17c2944afa494d42d3ad42929f3379842.tar.gz llvm-070848c17c2944afa494d42d3ad42929f3379842.tar.bz2 |
[AArch64][GISel] Don't pointlessly lower G_TRUNC (#81479)
If we have something like G_TRUNC from v2s32 to v2s16, then lowering
this to a concat of two G_TRUNC s32 to s16 followed by G_TRUNC from
v2s16 to v2s8 does not bring us any closer to legality. In fact, the
first part of that is a G_BUILD_VECTOR whose legalization will produce a
new G_TRUNC from v2s32 to v2s16, and both G_TRUNCs will then get
combined to the original, causing a legalization cycle.
Make the lowering condition more precise, by requiring that the original
vector is >128 bits, which is I believe the only case where this
specific splitting approach is useful.
Note that this doesn't actually produce a legal result (the alwaysLegal
is a lie, as before), but it will cause a proper globalisel abort
instead of an infinite legalization loop.
Fixes https://github.com/llvm/llvm-project/issues/81244.
Diffstat (limited to 'llvm/lib')
-rw-r--r-- | llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp index ab25e2b..933f13d 100644 --- a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp +++ b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp @@ -612,9 +612,8 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST) .lowerIf([=](const LegalityQuery &Query) { LLT DstTy = Query.Types[0]; LLT SrcTy = Query.Types[1]; - return DstTy.isVector() && (SrcTy.getSizeInBits() > 128 || - (DstTy.getScalarSizeInBits() * 2 < - SrcTy.getScalarSizeInBits())); + return DstTy.isVector() && SrcTy.getSizeInBits() > 128 && + DstTy.getScalarSizeInBits() * 2 <= SrcTy.getScalarSizeInBits(); }) .alwaysLegal(); |