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Make sure we don't promise alignments that are larger than the heap alignment to LLVM #56938

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Merged
merged 3 commits into from
Jan 3, 2025
Merged

Make sure we don't promise alignments that are larger than the heap alignment to LLVM #56938

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382c234
Make sure we don't promise alignments that are larger than the heap a…
gbaraldi Jan 2, 2025
6389a24
typo
oscardssmith Jan 2, 2025
2570e28
Fix broken test
gbaraldi Jan 3, 2025
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5 changes: 5 additions & 0 deletions Compiler/test/codegen.jl
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Expand Up @@ -1036,3 +1036,8 @@ f56739(a) where {T} = a
@test f56739(1) == 1
g56739(x) = @noinline f56739(x)
@test g56739(1) == 1

struct Vec56937 x::NTuple{8, VecElement{Int}} end

x56937 = Ref(Vec56937(ntuple(_->VecElement(1),8)))
@test x56937[].x[1] == VecElement{Int}(1) # shouldn't crash
2 changes: 2 additions & 0 deletions src/codegen.cpp
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Expand Up @@ -8916,6 +8916,8 @@ static jl_llvm_functions_t
Type *RT = Arg->getParamStructRetType();
TypeSize sz = DL.getTypeAllocSize(RT);
Align al = DL.getPrefTypeAlign(RT);
if (al > MAX_ALIGN)
al = Align(MAX_ALIGN);
Comment on lines 8917 to +8920
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Could we change these to use dereferenceable_size and julia_alignment functions? I usually distrust all DataLayout-based values, since they based on conversions to llvm types which require accuracy in first-class aggregates in matching C, which isn't entirely accurate

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I’ll give it a shot

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There doesn't seem to be a super precise type to get for all arguments sadly.

param.addAttribute(Attribute::NonNull);
// The `dereferenceable` below does not imply `nonnull` for non addrspace(0) pointers.
param.addDereferenceableAttr(sz);
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2 changes: 2 additions & 0 deletions src/datatype.c
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Expand Up @@ -769,6 +769,8 @@ void jl_compute_field_offsets(jl_datatype_t *st)
if (al > alignm)
alignm = al;
}
if (alignm > MAX_ALIGN)
alignm = MAX_ALIGN; // We cannot guarantee alignments over 16 bytes because that's what our heap is aligned as
if (LLT_ALIGN(sz, alignm) > sz) {
haspadding = 1;
sz = LLT_ALIGN(sz, alignm);
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