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Fix System V ABI for packed structs with misaligned fields #14324

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merged 1 commit into from
Feb 27, 2024
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Fix System V ABI for packed structs with misaligned fields #14324

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24 changes: 24 additions & 0 deletions spec/std/llvm/x86_64_abi_spec.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -144,6 +144,30 @@ class LLVM::ABI
info.arg_types[0].should eq(ArgType.indirect(str, Attribute::ByVal))
info.return_type.should eq(ArgType.indirect(str, Attribute::StructRet))
end

test "does with packed struct containing unaligned fields (#9873)" do |abi, ctx|
str = ctx.struct([ctx.int8, ctx.int16], packed: true)
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, Attribute::ByVal))
info.return_type.should eq(ArgType.indirect(str, Attribute::StructRet))
end

test "does with packed struct not containing unaligned fields" do |abi, ctx|
str = ctx.struct([ctx.int16, ctx.int8], packed: true)
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.direct(str, cast: ctx.struct([ctx.int64])))
info.return_type.should eq(ArgType.direct(str, cast: ctx.struct([ctx.int64])))
end
end
{% end %}
end
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12 changes: 11 additions & 1 deletion src/llvm/abi/x86_64.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,7 @@ class LLVM::ABI::X86_64 < LLVM::ABI
def classify(type)
words = (size(type) + 7) // 8
reg_classes = Array.new(words, RegClass::NoClass)
if words > 4
if words > 4 || has_misaligned_fields?(type)
all_mem(reg_classes)
else
classify(type, reg_classes, 0, 0)
Expand Down Expand Up @@ -275,6 +275,16 @@ class LLVM::ABI::X86_64 < LLVM::ABI
size(type, 8)
end

def has_misaligned_fields?(type : Type) : Bool
return false unless type.packed_struct?
offset = 0
type.struct_element_types.each do |elem|
return true unless offset.divisible_by?(align(elem))
offset += size(elem)
end
false
end

enum RegClass
NoClass
Int
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