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[SVE] Fix invalid usage of getNumElements() in InstCombineMulDivRem

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Summary:
getLogBase2 tries to iterate over the number of vector elements. Since
the number of elements of a scalable vector is unknown at compile time,
we must return null if the input type is scalable.

Identified by test LLVM.Transforms/InstCombine::nsw.ll

Reviewers: efriedma, fpetrogalli, kmclaughlin, spatel

Reviewed By: efriedma, fpetrogalli

Subscribers: tschuett, hiraditya, rkruppe, psnobl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79197
This commit is contained in:
Christopher Tetreault 2020-05-05 14:21:59 -07:00
parent 05620404c0
commit 9628857335
2 changed files with 33 additions and 4 deletions
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10
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -96,19 +96,21 @@ static Value *simplifyValueKnownNonZero(Value *V, InstCombiner &IC,
/// A helper routine of InstCombiner::visitMul().
///
/// If C is a scalar/vector of known powers of 2, then this function returns
/// a new scalar/vector obtained from logBase2 of C.
/// If C is a scalar/fixed width vector of known powers of 2, then this
/// function returns a new scalar/fixed width vector obtained from logBase2
/// of C.
/// Return a null pointer otherwise.
static Constant *getLogBase2(Type *Ty, Constant *C) {
const APInt *IVal;
if (match(C, m_APInt(IVal)) && IVal->isPowerOf2())
return ConstantInt::get(Ty, IVal->logBase2());
if (!Ty->isVectorTy())
// FIXME: We can extract pow of 2 of splat constant for scalable vectors.
if (!isa<FixedVectorType>(Ty))
return nullptr;
SmallVector<Constant *, 4> Elts;
for (unsigned I = 0, E = cast<VectorType>(Ty)->getNumElements(); I != E;
for (unsigned I = 0, E = cast<FixedVectorType>(Ty)->getNumElements(); I != E;
++I) {
Constant *Elt = C->getAggregateElement(I);
if (!Elt)

27
test/Transforms/InstCombine/udiv-pow2-vscale.ll Normal file
View File

@ -0,0 +1,27 @@
; RUN: opt -instcombine -S < %s | FileCheck %s
; This vscale udiv with a power-of-2 spalt on the rhs should not crash opt
; CHECK: define <vscale x 2 x i32> @udiv_pow2_vscale(<vscale x 2 x i32> %lhs)
define <vscale x 2 x i32> @udiv_pow2_vscale(<vscale x 2 x i32> %lhs) {
%splatter = insertelement <vscale x 2 x i32> undef, i32 2, i32 0
%rhs = shufflevector <vscale x 2 x i32> %splatter,
<vscale x 2 x i32> undef,
<vscale x 2 x i32> zeroinitializer
%res = udiv <vscale x 2 x i32> %lhs, %rhs
ret <vscale x 2 x i32> %res
}
; This fixed width udiv with a power-of-2 splat on the rhs should also not
; crash, and instcombine should eliminate the udiv
; CHECK-LABEL: define <2 x i32> @udiv_pow2_fixed(<2 x i32> %lhs)
; CHECK-NOT: udiv
define <2 x i32> @udiv_pow2_fixed(<2 x i32> %lhs) {
%splatter = insertelement <2 x i32> undef, i32 2, i32 0
%rhs = shufflevector <2 x i32> %splatter,
<2 x i32> undef,
<2 x i32> zeroinitializer
%res = udiv <2 x i32> %lhs, %rhs
ret <2 x i32> %res
}