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X86 64 abi misaligned packed #16667

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419c0b7
Add test for non-packed struct containing packed struct with unaligne…
kojix2 Feb 23, 2026
7f636bd
Fix out-of-bounds in misaligned field classification
kojix2 Feb 23, 2026
4cba992
Add test for non-packed struct containing array of packed struct with…
kojix2 Feb 23, 2026
31e70d3
Fix misaligned field detection for nested struct and array
kojix2 Feb 23, 2026
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26 changes: 26 additions & 0 deletions spec/compiler/codegen/abi/x86_64_spec.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,32 @@ class Crystal::ABI
info.arg_types[0].should eq(ArgType.indirect(str, LLVM::Attribute::ByVal))
info.return_type.should eq(ArgType.indirect(str, LLVM::Attribute::StructRet))
end

test "does with non-packed struct containing packed struct with unaligned fields" do |abi, ctx|
inner = ctx.struct([ctx.int16, ctx.int8], packed: true)
str = ctx.struct([ctx.int8, inner])
arg_types = [str]
return_type = str

info = abi.abi_info(arg_types, return_type, true, ctx)
info.arg_types.size.should eq(1)

info.arg_types[0].should eq(ArgType.indirect(str, LLVM::Attribute::ByVal))
info.return_type.should eq(ArgType.indirect(str, LLVM::Attribute::StructRet))
end

test "does with non-packed struct containing single-element array of packed struct with unaligned fields" do |abi, ctx|
inner = ctx.struct([ctx.int16, ctx.int8], packed: true).array(1)
str = ctx.struct([ctx.int8, inner])
arg_types = [str]
return_type = str

info = abi.abi_info(arg_types, return_type, true, ctx)
info.arg_types.size.should eq(1)

info.arg_types[0].should eq(ArgType.indirect(str, LLVM::Attribute::ByVal))
info.return_type.should eq(ArgType.indirect(str, LLVM::Attribute::StructRet))
end
end
{% end %}
end
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7 changes: 4 additions & 3 deletions src/compiler/crystal/codegen/abi/x86_64.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -118,7 +118,7 @@ class Crystal::ABI::X86_64 < Crystal::ABI
i = off // 8
e = (off + t_size + 7) // 8
while i < e
unify(cls, ix + 1, RegClass::Memory)
unify(cls, ix + i, RegClass::Memory)
i += 1
end
return
Expand Down Expand Up @@ -278,9 +278,10 @@ class Crystal::ABI::X86_64 < Crystal::ABI
def has_misaligned_fields?(type : LLVM::Type, offset : Int = 0) : Bool
case type.kind
when LLVM::Type::Kind::Struct
return false unless type.packed_struct?
type.struct_element_types.each do |elem|
offset = align_offset(offset, elem) unless type.packed_struct?
return true unless offset.divisible_by?(align(elem))
return true if has_misaligned_fields?(elem, offset)
offset += size(elem)
end
false
Expand All @@ -301,7 +302,7 @@ class Crystal::ABI::X86_64 < Crystal::ABI
# misaligned fields, then `size(elem) % align(elem) == 0` must be true,
# meaning array indices have no effect on element alignment.
elem = type.element_type
has_misaligned_fields?(elem) || type.array_size > 1 && has_misaligned_fields?(elem, size(elem))
has_misaligned_fields?(elem, offset) || type.array_size > 1 && has_misaligned_fields?(elem, offset + size(elem))
else
false
end
Expand Down
7 changes: 4 additions & 3 deletions src/llvm/abi/x86_64.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -119,7 +119,7 @@ class LLVM::ABI::X86_64 < LLVM::ABI
i = off // 8
e = (off + t_size + 7) // 8
while i < e
unify(cls, ix + 1, RegClass::Memory)
unify(cls, ix + i, RegClass::Memory)
i += 1
end
return
Expand Down Expand Up @@ -279,9 +279,10 @@ class LLVM::ABI::X86_64 < LLVM::ABI
def has_misaligned_fields?(type : Type, offset : Int = 0) : Bool
case type.kind
when Type::Kind::Struct
return false unless type.packed_struct?
type.struct_element_types.each do |elem|
offset = align_offset(offset, elem) unless type.packed_struct?
return true unless offset.divisible_by?(align(elem))
return true if has_misaligned_fields?(elem, offset)
offset += size(elem)
end
false
Expand All @@ -302,7 +303,7 @@ class LLVM::ABI::X86_64 < LLVM::ABI
# misaligned fields, then `size(elem) % align(elem) == 0` must be true,
# meaning array indices have no effect on element alignment.
elem = type.element_type
has_misaligned_fields?(elem) || type.array_size > 1 && has_misaligned_fields?(elem, size(elem))
has_misaligned_fields?(elem, offset) || type.array_size > 1 && has_misaligned_fields?(elem, offset + size(elem))
else
false
end
Expand Down
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