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[AArch64] Further restricts when a dup(*ext) can be rearranged

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In most cases, the dup(*ext) pattern can be rearranged to perform
the extension on the vector side, allowing for further vector-specific
optimisations to be made. However the initial checks for this conversion
were insufficient, allowing invalid encodings to be attempted (causing
compilation to fail).

Differential Revision: https://reviews.llvm.org/D94778
This commit is contained in:
Nicholas Guy
2021-01-15 14:26:51 +00:00
parent d806618636
commit f5fcbe4e3c
2 changed files with 37 additions and 4 deletions
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8
llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
View File

@@ -11843,7 +11843,8 @@ static SDValue performCommonVectorExtendCombine(SDValue VectorShuffle,
SDValue InsertVectorNode = DAG.getNode(
InsertVectorElt.getOpcode(), DL, PreExtendVT, DAG.getUNDEF(PreExtendVT),
Extend.getOperand(0), DAG.getConstant(0, DL, MVT::i64));
DAG.getAnyExtOrTrunc(Extend.getOperand(0), DL, PreExtendType),
DAG.getConstant(0, DL, MVT::i64));
std::vector<int> ShuffleMask(TargetType.getVectorElementCount().getValue());
@@ -11851,9 +11852,8 @@ static SDValue performCommonVectorExtendCombine(SDValue VectorShuffle,
DAG.getVectorShuffle(PreExtendVT, DL, InsertVectorNode,
DAG.getUNDEF(PreExtendVT), ShuffleMask);
SDValue ExtendNode =
DAG.getNode(IsSExt ? ISD::SIGN_EXTEND : ISD::ZERO_EXTEND, DL, TargetType,
VectorShuffleNode, DAG.getValueType(TargetType));
SDValue ExtendNode = DAG.getNode(IsSExt ? ISD::SIGN_EXTEND : ISD::ZERO_EXTEND,
DL, TargetType, VectorShuffleNode);
return ExtendNode;
}

33
llvm/test/CodeGen/AArch64/aarch64-dup-ext-crash.ll Normal file
View File

@@ -0,0 +1,33 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -o -| FileCheck %s
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-unknown-linux-gnu"
; This test covers a case where an AArch64 DUP instruction is generated with an
; invalid encoding, resulting in a crash. We don't care about the specific output
; here, only that this case no longer causes said crash.
define dso_local i32 @dupext_crashtest(i32 %e) local_unnamed_addr {
; CHECK-LABEL: dupext_crashtest:
for.body.lr.ph:
%conv314 = zext i32 %e to i64
br label %vector.memcheck
vector.memcheck: ; preds = %for.body.lr.ph
br label %vector.ph
vector.ph: ; preds = %vector.memcheck
%broadcast.splatinsert = insertelement <2 x i64> poison, i64 %conv314, i32 0
%broadcast.splat = shufflevector <2 x i64> %broadcast.splatinsert, <2 x i64> poison, <2 x i32> zeroinitializer
br label %vector.body
vector.body: ; preds = %vector.body, %vector.ph
%wide.load = load <2 x i32>, <2 x i32>* undef, align 4
%0 = zext <2 x i32> %wide.load to <2 x i64>
%1 = mul nuw <2 x i64> %broadcast.splat, %0
%2 = trunc <2 x i64> %1 to <2 x i32>
%3 = select <2 x i1> undef, <2 x i32> undef, <2 x i32> %2
%4 = bitcast i32* undef to <2 x i32>*
store <2 x i32> %3, <2 x i32>* %4, align 4
br label %vector.body
}