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[InterleavedAccessPass] Don't increase the number of bytes loaded.

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Even if the interleaving transform would otherwise be legal, we shouldn't
introduce an interleaved load that is wider than the original load: it might
have undefined behavior.

It might be possible to perform some sort of mask-narrowing transform in
some cases (using a narrower interleaved load, then extending the
results using shufflevectors).  But I haven't tried to implement that,
at least for now.

Fixes https://bugs.llvm.org/show_bug.cgi?id=41245 .

Differential Revision: https://reviews.llvm.org/D59954

llvm-svn: 357212
This commit is contained in:
Eli Friedman 2019-03-28 20:44:50 +00:00
parent 4959350890
commit 5212b768f5
2 changed files with 28 additions and 9 deletions
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12
lib/CodeGen/InterleavedAccessPass.cpp
View File

@ -163,14 +163,19 @@ static bool isDeInterleaveMaskOfFactor(ArrayRef<int> Mask, unsigned Factor,
/// <0, 2, 4, 6> (mask of index 0 to extract even elements)
/// <1, 3, 5, 7> (mask of index 1 to extract odd elements)
static bool isDeInterleaveMask(ArrayRef<int> Mask, unsigned &Factor,
unsigned &Index, unsigned MaxFactor) {
unsigned &Index, unsigned MaxFactor,
unsigned NumLoadElements) {
if (Mask.size() < 2)
return false;
// Check potential Factors.
for (Factor = 2; Factor <= MaxFactor; Factor++)
for (Factor = 2; Factor <= MaxFactor; Factor++) {
// Make sure we don't produce a load wider than the input load.
if (Mask.size() * Factor > NumLoadElements)
return false;
if (isDeInterleaveMaskOfFactor(Mask, Factor, Index))
return true;
}
return false;
}
@ -302,9 +307,10 @@ bool InterleavedAccess::lowerInterleavedLoad(
unsigned Factor, Index;
unsigned NumLoadElements = LI->getType()->getVectorNumElements();
// Check if the first shufflevector is DE-interleave shuffle.
if (!isDeInterleaveMask(Shuffles[0]->getShuffleMask(), Factor, Index,
MaxFactor))
MaxFactor, NumLoadElements))
return false;
// Holds the corresponding index for each DE-interleave shuffle.

25
test/Transforms/InterleavedAccess/ARM/interleaved-accesses.ll
View File

@ -352,9 +352,9 @@ define void @store_undef_mask_factor4(<16 x i32>* %ptr, <4 x i32> %v0, <4 x i32>
ret void
}
define void @load_address_space(<4 x i32> addrspace(1)* %ptr) {
define void @load_address_space(<8 x i32> addrspace(1)* %ptr) {
; NEON-LABEL: @load_address_space(
; NEON-NEXT: [[TMP1:%.*]] = bitcast <4 x i32> addrspace(1)* %ptr to i8 addrspace(1)*
; NEON-NEXT: [[TMP1:%.*]] = bitcast <8 x i32> addrspace(1)* %ptr to i8 addrspace(1)*
; NEON-NEXT: [[VLDN:%.*]] = call { <2 x i32>, <2 x i32>, <2 x i32> } @llvm.arm.neon.vld3.v2i32.p1i8(i8 addrspace(1)* [[TMP1]], i32 0)
; NEON-NEXT: [[TMP2:%.*]] = extractvalue { <2 x i32>, <2 x i32>, <2 x i32> } [[VLDN]], 2
; NEON-NEXT: [[TMP3:%.*]] = extractvalue { <2 x i32>, <2 x i32>, <2 x i32> } [[VLDN]], 1
@ -364,10 +364,10 @@ define void @load_address_space(<4 x i32> addrspace(1)* %ptr) {
; NO_NEON-NOT: @llvm.arm.neon
; NO_NEON: ret void
;
%interleaved.vec = load <4 x i32>, <4 x i32> addrspace(1)* %ptr
%v0 = shufflevector <4 x i32> %interleaved.vec, <4 x i32> undef, <2 x i32> <i32 0, i32 3>
%v1 = shufflevector <4 x i32> %interleaved.vec, <4 x i32> undef, <2 x i32> <i32 1, i32 4>
%v2 = shufflevector <4 x i32> %interleaved.vec, <4 x i32> undef, <2 x i32> <i32 2, i32 5>
%interleaved.vec = load <8 x i32>, <8 x i32> addrspace(1)* %ptr
%v0 = shufflevector <8 x i32> %interleaved.vec, <8 x i32> undef, <2 x i32> <i32 0, i32 3>
%v1 = shufflevector <8 x i32> %interleaved.vec, <8 x i32> undef, <2 x i32> <i32 1, i32 4>
%v2 = shufflevector <8 x i32> %interleaved.vec, <8 x i32> undef, <2 x i32> <i32 2, i32 5>
ret void
}
@ -883,3 +883,16 @@ define void @load_factor2_wide_pointer(<16 x i32*>* %ptr) {
%v1 = shufflevector <16 x i32*> %interleaved.vec, <16 x i32*> undef, <8 x i32> <i32 1, i32 3, i32 5, i32 7, i32 9, i32 11, i32 13, i32 15>
ret void
}
; This would be a candidate for interleaving, except that load doesn't
; actually load enough elements to satisfy the shuffle masks. (It would be
; possible to produce a vld2.v2i32, but that currently isn't implemented.)
define void @load_out_of_range(<4 x i32>* %ptr) {
; ALL-LABEL: @load_out_of_range(
; ALL-NOT: @llvm.arm.neon
; ALL: ret void
%interleaved.vec = load <4 x i32>, <4 x i32>* %ptr, align 4
%v0 = shufflevector <4 x i32> %interleaved.vec, <4 x i32> undef, <4 x i32> <i32 0, i32 2, i32 undef, i32 undef>
%v1 = shufflevector <4 x i32> %interleaved.vec, <4 x i32> undef, <4 x i32> <i32 1, i32 3, i32 undef, i32 undef>
ret void
}