[LLVMdev] Linking opaque types

Wed Jul 27 19:23:49 PDT 2011

>
> I'm not sure what you mean.  LLVM is perfectly fine with opaque structs so
> long as you don't "deference" them, GEP into them, need their size, etc.
>

Now that I've actually got my library to link, let's look at the result -
here's a small section of the llvm-dis output (I've sorted the lines to make
my point):

%"tart.collections.Collection[tart.core.Attribute]" = type {
%"tart.core.Iterable[tart.core.Attribute]", %tart.core.TypeInfoBlock.122* }
%"tart.collections.Collection[tart.core.Object]" = type {
%"tart.core.Iterable[tart.core.Object]", %tart.core.TypeInfoBlock* }
%"tart.collections.Collection[tart.core.Object].1358" = type {
%"tart.core.Iterable[tart.core.Object].1357", %tart.core.TypeInfoBlock.1372*
}
%"tart.collections.Collection[tart.core.Object].145" = type {
%"tart.core.Iterable[tart.core.Object].144", %tart.core.TypeInfoBlock.122* }
%"tart.collections.Collection[tart.core.Object].1664" = type {
%"tart.core.Iterable[tart.core.Object].1663", %tart.core.TypeInfoBlock.1678*
}
%"tart.collections.Collection[tart.core.Object].1890" = type {
%"tart.core.Iterable[tart.core.Object].1889", %tart.core.TypeInfoBlock.1904*
}
%"tart.collections.Collection[tart.core.Object].220" = type {
%"tart.core.Iterable[tart.core.Object].219", %tart.core.TypeInfoBlock.234* }
%"tart.collections.Collection[tart.core.Object].32" = type {
%"tart.core.Iterable[tart.core.Object].31", %tart.core.TypeInfoBlock.46* }
%"tart.collections.Collection[tart.core.Object].3359" = type {
%"tart.core.Iterable[tart.core.Object].3358", %tart.core.TypeInfoBlock.3373*
}
%"tart.collections.Collection[tart.core.Object].427" = type {
%"tart.core.Iterable[tart.core.Object].426", %tart.core.TypeInfoBlock.441* }
%"tart.collections.Collection[tart.core.Object].454" = type {
%"tart.core.Iterable[tart.core.Object].453", %tart.core.TypeInfoBlock.468* }
%"tart.collections.Collection[tart.core.Object].5" = type {
%"tart.core.Iterable[tart.core.Object].4", %tart.core.TypeInfoBlock.19* }
%"tart.collections.Collection[tart.core.Object].59" = type {
%"tart.core.Iterable[tart.core.Object].58", %tart.core.TypeInfoBlock.73* }
%"tart.collections.Collection[tart.core.Object].716" = type {
%"tart.core.Iterable[tart.core.Object].715", %tart.core.TypeInfoBlock.730* }
%"tart.collections.Collection[tart.core.Object].796" = type {
%"tart.core.Iterable[tart.core.Object].795", %tart.core.TypeInfoBlock.810* }
%"tart.collections.Collection[tart.core.Object].86" = type {
%"tart.core.Iterable[tart.core.Object].85", %tart.core.TypeInfoBlock.100* }
%"tart.collections.Collection[tart.core.String]" = type {
%"tart.core.Iterable[tart.core.String]", %tart.core.TypeInfoBlock.122* }
%"tart.collections.Collection[tart.core.String|Null]" = type {
%"tart.core.Iterable[tart.core.String|Null]", %tart.core.TypeInfoBlock.122*
}
%"tart.collections.Collection[tart.reflect.Field]" = type {
%"tart.core.Iterable[tart.reflect.Field]", %tart.core.TypeInfoBlock* }
%"tart.collections.Collection[tart.reflect.Field].1361" = type {
%"tart.core.Iterable[tart.reflect.Field].1360",
%tart.core.TypeInfoBlock.1372* }
%"tart.collections.Collection[tart.reflect.Field].148" = type {
%"tart.core.Iterable[tart.reflect.Field].147", %tart.core.TypeInfoBlock.122*
}
%"tart.collections.Collection[tart.reflect.Field].1667" = type {
%"tart.core.Iterable[tart.reflect.Field].1666",
%tart.core.TypeInfoBlock.1678* }
%"tart.collections.Collection[tart.reflect.Field].1893" = type {
%"tart.core.Iterable[tart.reflect.Field].1892",
%tart.core.TypeInfoBlock.1904* }
%"tart.collections.Collection[tart.reflect.Field].223" = type {
%"tart.core.Iterable[tart.reflect.Field].222", %tart.core.TypeInfoBlock.234*
}
%"tart.collections.Collection[tart.reflect.Field].3362" = type {
%"tart.core.Iterable[tart.reflect.Field].3361",
%tart.core.TypeInfoBlock.3373* }
%"tart.collections.Collection[tart.reflect.Field].35" = type {
%"tart.core.Iterable[tart.reflect.Field].34", %tart.core.TypeInfoBlock.46* }
%"tart.collections.Collection[tart.reflect.Field].430" = type {
%"tart.core.Iterable[tart.reflect.Field].429", %tart.core.TypeInfoBlock.441*
}
%"tart.collections.Collection[tart.reflect.Field].457" = type {
%"tart.core.Iterable[tart.reflect.Field].456", %tart.core.TypeInfoBlock.468*
}
%"tart.collections.Collection[tart.reflect.Field].62" = type {
%"tart.core.Iterable[tart.reflect.Field].61", %tart.core.TypeInfoBlock.73* }
%"tart.collections.Collection[tart.reflect.Field].719" = type {
%"tart.core.Iterable[tart.reflect.Field].718", %tart.core.TypeInfoBlock.730*
}
%"tart.collections.Collection[tart.reflect.Field].799" = type {
%"tart.core.Iterable[tart.reflect.Field].798", %tart.core.TypeInfoBlock.810*
}
%"tart.collections.Collection[tart.reflect.Field].8" = type {
%"tart.core.Iterable[tart.reflect.Field].7", %tart.core.TypeInfoBlock.19* }
%"tart.collections.Collection[tart.reflect.Field].89" = type {
%"tart.core.Iterable[tart.reflect.Field].88", %tart.core.TypeInfoBlock.100*
}
%"tart.collections.Collection[tart.reflect.Method]" = type {
%"tart.core.Iterable[tart.reflect.Method]", %tart.core.TypeInfoBlock* }
%"tart.collections.Collection[tart.reflect.Method].1367" = type {
%"tart.core.Iterable[tart.reflect.Method].1366",
%tart.core.TypeInfoBlock.1372* }
%"tart.collections.Collection[tart.reflect.Method].14" = type {
%"tart.core.Iterable[tart.reflect.Method].13", %tart.core.TypeInfoBlock.19*
}
%"tart.collections.Collection[tart.reflect.Method].154" = type {
%"tart.core.Iterable[tart.reflect.Method].153",
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Collection[tart.reflect.Method].1673" = type {
%"tart.core.Iterable[tart.reflect.Method].1672",
%tart.core.TypeInfoBlock.1678* }
%"tart.collections.Collection[tart.reflect.Method].1899" = type {
%"tart.core.Iterable[tart.reflect.Method].1898",
%tart.core.TypeInfoBlock.1904* }
%"tart.collections.Collection[tart.reflect.Method].229" = type {
%"tart.core.Iterable[tart.reflect.Method].228",
%tart.core.TypeInfoBlock.234* }
%"tart.collections.Collection[tart.reflect.Method].3368" = type {
%"tart.core.Iterable[tart.reflect.Method].3367",
%tart.core.TypeInfoBlock.3373* }
%"tart.collections.Collection[tart.reflect.Method].41" = type {
%"tart.core.Iterable[tart.reflect.Method].40", %tart.core.TypeInfoBlock.46*
}
%"tart.collections.Collection[tart.reflect.Method].436" = type {
%"tart.core.Iterable[tart.reflect.Method].435",
%tart.core.TypeInfoBlock.441* }
%"tart.collections.Collection[tart.reflect.Method].463" = type {
%"tart.core.Iterable[tart.reflect.Method].462",
%tart.core.TypeInfoBlock.468* }
%"tart.collections.Collection[tart.reflect.Method].68" = type {
%"tart.core.Iterable[tart.reflect.Method].67", %tart.core.TypeInfoBlock.73*
}
%"tart.collections.Collection[tart.reflect.Method].725" = type {
%"tart.core.Iterable[tart.reflect.Method].724",
%tart.core.TypeInfoBlock.730* }
%"tart.collections.Collection[tart.reflect.Method].805" = type {
%"tart.core.Iterable[tart.reflect.Method].804",
%tart.core.TypeInfoBlock.810* }
%"tart.collections.Collection[tart.reflect.Method].95" = type {
%"tart.core.Iterable[tart.reflect.Method].94", %tart.core.TypeInfoBlock.100*
}
%"tart.collections.Collection[tart.reflect.Module]" = type {
%"tart.core.Iterable[tart.reflect.Module]", %tart.core.TypeInfoBlock.122* }
%"tart.collections.Collection[tart.reflect.NameTable.CompoundName]" = type {
%"tart.core.Iterable[tart.reflect.NameTable.CompoundName]",
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Collection[tart.reflect.Package]" = type {
%"tart.core.Iterable[tart.reflect.Package]", %tart.core.TypeInfoBlock.122* }
%"tart.collections.Collection[tart.reflect.Parameter]" = type {
%"tart.core.Iterable[tart.reflect.Parameter]", %tart.core.TypeInfoBlock.122*
}
%"tart.collections.Collection[tart.reflect.Property]" = type {
%"tart.core.Iterable[tart.reflect.Property]", %tart.core.TypeInfoBlock* }
%"tart.collections.Collection[tart.reflect.Property].11" = type {
%"tart.core.Iterable[tart.reflect.Property].10",
%tart.core.TypeInfoBlock.19* }
%"tart.collections.Collection[tart.reflect.Property].1364" = type {
%"tart.core.Iterable[tart.reflect.Property].1363",
%tart.core.TypeInfoBlock.1372* }
%"tart.collections.Collection[tart.reflect.Property].151" = type {
%"tart.core.Iterable[tart.reflect.Property].150",
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Collection[tart.reflect.Property].1670" = type {
%"tart.core.Iterable[tart.reflect.Property].1669",
%tart.core.TypeInfoBlock.1678* }
%"tart.collections.Collection[tart.reflect.Property].1896" = type {
%"tart.core.Iterable[tart.reflect.Property].1895",
%tart.core.TypeInfoBlock.1904* }
%"tart.collections.Collection[tart.reflect.Property].226" = type {
%"tart.core.Iterable[tart.reflect.Property].225",
%tart.core.TypeInfoBlock.234* }
%"tart.collections.Collection[tart.reflect.Property].3365" = type {
%"tart.core.Iterable[tart.reflect.Property].3364",
%tart.core.TypeInfoBlock.3373* }
%"tart.collections.Collection[tart.reflect.Property].38" = type {
%"tart.core.Iterable[tart.reflect.Property].37",
%tart.core.TypeInfoBlock.46* }
%"tart.collections.Collection[tart.reflect.Property].433" = type {
%"tart.core.Iterable[tart.reflect.Property].432",
%tart.core.TypeInfoBlock.441* }
%"tart.collections.Collection[tart.reflect.Property].460" = type {
%"tart.core.Iterable[tart.reflect.Property].459",
%tart.core.TypeInfoBlock.468* }
%"tart.collections.Collection[tart.reflect.Property].65" = type {
%"tart.core.Iterable[tart.reflect.Property].64",
%tart.core.TypeInfoBlock.73* }
%"tart.collections.Collection[tart.reflect.Property].722" = type {
%"tart.core.Iterable[tart.reflect.Property].721",
%tart.core.TypeInfoBlock.730* }
%"tart.collections.Collection[tart.reflect.Property].802" = type {
%"tart.core.Iterable[tart.reflect.Property].801",
%tart.core.TypeInfoBlock.810* }
%"tart.collections.Collection[tart.reflect.Property].92" = type {
%"tart.core.Iterable[tart.reflect.Property].91",
%tart.core.TypeInfoBlock.100* }
%"tart.collections.Collection[tart.reflect.Type]" = type {
%"tart.core.Iterable[tart.reflect.Type]", %tart.core.TypeInfoBlock* }
%"tart.collections.Collection[tart.reflect.Type].1355" = type {
%"tart.core.Iterable[tart.reflect.Type].1354",
%tart.core.TypeInfoBlock.1372* }
%"tart.collections.Collection[tart.reflect.Type].142" = type {
%"tart.core.Iterable[tart.reflect.Type].141", %tart.core.TypeInfoBlock.122*
}
%"tart.collections.Collection[tart.reflect.Type].1661" = type {
%"tart.core.Iterable[tart.reflect.Type].1660",
%tart.core.TypeInfoBlock.1678* }
%"tart.collections.Collection[tart.reflect.Type].1887" = type {
%"tart.core.Iterable[tart.reflect.Type].1886",
%tart.core.TypeInfoBlock.1904* }
%"tart.collections.Collection[tart.reflect.Type].2" = type {
%"tart.core.Iterable[tart.reflect.Type].1", %tart.core.TypeInfoBlock.19* }
%"tart.collections.Collection[tart.reflect.Type].217" = type {
%"tart.core.Iterable[tart.reflect.Type].216", %tart.core.TypeInfoBlock.234*
}
%"tart.collections.Collection[tart.reflect.Type].29" = type {
%"tart.core.Iterable[tart.reflect.Type].28", %tart.core.TypeInfoBlock.46* }
%"tart.collections.Collection[tart.reflect.Type].3356" = type {
%"tart.core.Iterable[tart.reflect.Type].3355",
%tart.core.TypeInfoBlock.3373* }
%"tart.collections.Collection[tart.reflect.Type].424" = type {
%"tart.core.Iterable[tart.reflect.Type].423", %tart.core.TypeInfoBlock.441*
}
%"tart.collections.Collection[tart.reflect.Type].451" = type {
%"tart.core.Iterable[tart.reflect.Type].450", %tart.core.TypeInfoBlock.468*
}
%"tart.collections.Collection[tart.reflect.Type].56" = type {
%"tart.core.Iterable[tart.reflect.Type].55", %tart.core.TypeInfoBlock.73* }
%"tart.collections.Collection[tart.reflect.Type].713" = type {
%"tart.core.Iterable[tart.reflect.Type].712", %tart.core.TypeInfoBlock.730*
}
%"tart.collections.Collection[tart.reflect.Type].793" = type {
%"tart.core.Iterable[tart.reflect.Type].792", %tart.core.TypeInfoBlock.810*
}
%"tart.collections.Collection[tart.reflect.Type].83" = type {
%"tart.core.Iterable[tart.reflect.Type].82", %tart.core.TypeInfoBlock.100* }
%"tart.collections.Collection[uint8]" = type { %"tart.core.Iterable[uint8]",
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[char]" = type { %tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[int8]" = type { %tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[tart.core.Attribute]" = type {
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[tart.core.Object]" = type {
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[tart.core.String]" = type {
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[tart.core.String].2484" = type {
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[tart.core.String|Null]" = type {
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[tart.reflect.Module]" = type {
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[tart.reflect.NameTable.CompoundName]" = type {
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[tart.reflect.Package]" = type {
%tart.core.TypeInfoBlock.122* }
%"tart.collections.Copyable[uint8]" = type { %tart.core.TypeInfoBlock.122* }
%"tart.collections.ImmutableList[tart.core.String]" = type {
%tart.core.Object, %"tart.core.String[]"* }
%"tart.collections.ImmutableList[tart.core.String].103" = type {
%tart.core.Object.101, %"tart.core.String[].102"* }
%"tart.collections.ImmutableList[tart.core.String].110" = type {
%tart.core.Object.108, %"tart.core.String[].135"* }
%"tart.collections.ImmutableList[tart.core.String].1269" = type opaque
%"tart.collections.ImmutableList[tart.core.String].128" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1375" = type {
%tart.core.Object.1373, %"tart.core.String[].1374"* }
%"tart.collections.ImmutableList[tart.core.String].1425" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1434" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1443" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1491" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1500" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1509" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1518" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1527" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1611" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1620" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1629" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1638" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1647" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1681" = type {
%tart.core.Object.1679, %"tart.core.String[].1680"* }
%"tart.collections.ImmutableList[tart.core.String].172" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1762" = type opaque
%"tart.collections.ImmutableList[tart.core.String].1907" = type {
%tart.core.Object.1905, %"tart.core.String[].1906"* }
%"tart.collections.ImmutableList[tart.core.String].2081" = type opaque
%"tart.collections.ImmutableList[tart.core.String].2098" = type opaque
%"tart.collections.ImmutableList[tart.core.String].2107" = type opaque
%"tart.collections.ImmutableList[tart.core.String].22" = type {
%tart.core.Object.20, %"tart.core.String[].21"* }
%"tart.collections.ImmutableList[tart.core.String].237" = type {
%tart.core.Object.235, %"tart.core.String[].236"* }
%"tart.collections.ImmutableList[tart.core.String].282" = type opaque
%"tart.collections.ImmutableList[tart.core.String].3376" = type {
%tart.core.Object.3374, %"tart.core.String[].3375"* }
%"tart.collections.ImmutableList[tart.core.String].3506" = type opaque
%"tart.collections.ImmutableList[tart.core.String].3523" = type opaque
%"tart.collections.ImmutableList[tart.core.String].3559" = type opaque
%"tart.collections.ImmutableList[tart.core.String].444" = type {
%tart.core.Object.442, %"tart.core.String[].443"* }
%"tart.collections.ImmutableList[tart.core.String].471" = type {
%tart.core.Object.469, %"tart.core.String[].470"* }
%"tart.collections.ImmutableList[tart.core.String].481" = type opaque
%"tart.collections.ImmutableList[tart.core.String].49" = type {
%tart.core.Object.47, %"tart.core.String[].48"* }
%"tart.collections.ImmutableList[tart.core.String].689" = type opaque
%"tart.collections.ImmutableList[tart.core.String].698" = type opaque
%"tart.collections.ImmutableList[tart.core.String].707" = type opaque
%"tart.collections.ImmutableList[tart.core.String].733" = type {
%tart.core.Object.731, %"tart.core.String[].732"* }
%"tart.collections.ImmutableList[tart.core.String].743" = type opaque
%"tart.collections.ImmutableList[tart.core.String].76" = type {
%tart.core.Object.74, %"tart.core.String[].75"* }
%"tart.collections.ImmutableList[tart.core.String].787" = type opaque
%"tart.collections.ImmutableList[tart.core.String].813" = type {
%tart.core.Object.811, %"tart.core.String[].812"* }
%"tart.collections.ImmutableList[tart.core.String].969" = type opaque

As you can see, for each original source type, there are generally around
10-30 duplicates. This tells me that the IR is far less clear or compact
than it ought to be. In fact it looks like an explosion of type names.

For example, as you can see there are a ton of definitions of
"tart.core.ImmutableList[String]", many of which are opaque - why was the
linker not able to merge these?

Bear in mind that this is a "headerless" language, like Java and Python,
where there is a mapping between the directory structure containing the
source files, and the type naming hierarchy within the language. What this
basically means is that for any given type name, there is one true
definition of that type, and it's generally impossible, or at least very
difficult, to have two incompatible definitions of the same type.

This does not mean, however, that the compiler emits identical definitions
for a particular type name in every module. In order to prevent the problem
I was talking about with the previous type system - where the compiler is
forced to "drill down" through pointer fields - the compiler only does a
StructType.setBody() when it is actually needed. If a given pointer field is
never dereferenced, then the type that is pointed to remains opaque.

However, I would expect that two types which have the same name and the
similar structure to be merged - even if some of the fields of the two types
are pointers to opaque types, as long as the type name of the field is the
same in both cases.

-- 
-- Talin
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