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https://github.com/carbon-language/carbon-lang.git
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David BlaikieandDana Jansens
a179bd461b
This adds just enough debug info for i32/int parameters and return
values, with a path forward for adding DWARF type metadata for other
types.
As it happens, return type information is carried separately from
parameter information:
* Return type information is carried in the `type` of the `DISubprogram`
(as a `DISubroutineType` - which does carry parameter type information
as well, but that's unused when the DWARF is emitted by LLVM)
* Parameter information is carried by `DILocalVariable`s with a non-zero
`arg` value (representing the order of function parameters)
In the absence of locations for the parameters (future work), nothing
would usually keep the `DILocalVariable` live/reachable when emitting
DWARF - so for cases where this can happen (for clang, this happens in
optimized builds where all references to the parameter variable might be
optimized away) the variables can be "retained" in a list on the
`DISubprogram` - achieved by passing `AlwaysPreserve` parameter to
`createParameterVariable` (adds them to a list, then that list gets
attached to the `DISubprogram` when it's finalized later)
For now, any unsupported types are emitted as `void*` (except void
return, which is implemented as void) as a placeholder.
Given this example:
```
import Core library "io";
class MyClass {
}
fn Unsupported(v: MyClass) {
}
fn Ret() -> i32 {
return 42;
}
fn Arg(x: i32) {
Core.Print(x);
}
fn Run() {
}
```
this is the resulting DWARF:
```
DW_TAG_compile_unit
DW_AT_name ("test.carbon")
DW_TAG_subprogram
DW_AT_name ("Unsupported")
DW_TAG_formal_parameter
DW_AT_type (0x00000066 "void *")
DW_TAG_subprogram
DW_AT_name ("Ret")
DW_AT_type (0x00000062 "int")
DW_TAG_subprogram
DW_AT_name ("Arg")
DW_TAG_formal_parameter
DW_AT_type (0x00000062 "int")
DW_TAG_subprogram
DW_AT_name ("Run")
DW_TAG_base_type
DW_AT_name ("int")
DW_TAG_pointer_type
```
And the debugger:
```
(gdb) p Ret()
$1 = 42
(gdb) p Arg(4)
4
$2 = void
```
I'm not sure if there's a way this logic should be merged with the logic
for making the `llvm::Function` type (which the `DISubroutineType`
building code was inspired by/copied from) - since they're done at
different times/places, I don't think there's an easy way to do it in
one pass, but maybe the code can be shared (even if it's run twice) in
some generic `SemIR::Function` type walker.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
58 lines
2.5 KiB
Plaintext
58 lines
2.5 KiB
Plaintext
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/int.carbon
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//
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// AUTOUPDATE
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// TIP: To test this file alone, run:
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// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/class/method.carbon
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// TIP: To dump output, run:
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// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/class/method.carbon
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class C {
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var a: i32;
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fn Get[self: C]() -> i32;
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fn Set[ref self: C](n: i32);
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}
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fn F(p: C*) {
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let n: i32 = (*p).Get();
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(*p).Set(n);
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}
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// CHECK:STDOUT: ; ModuleID = 'method.carbon'
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// CHECK:STDOUT: source_filename = "method.carbon"
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// CHECK:STDOUT:
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// CHECK:STDOUT: declare i32 @_CGet.C.Main(ptr)
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// CHECK:STDOUT:
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// CHECK:STDOUT: declare void @_CSet.C.Main(ptr, i32)
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// CHECK:STDOUT:
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// CHECK:STDOUT: ; Function Attrs: nounwind
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// CHECK:STDOUT: define void @_CF.Main(ptr %p) #0 !dbg !4 {
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// CHECK:STDOUT: entry:
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// CHECK:STDOUT: %C.Get.call = call i32 @_CGet.C.Main(ptr %p), !dbg !10
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// CHECK:STDOUT: call void @_CSet.C.Main(ptr %p, i32 %C.Get.call), !dbg !11
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// CHECK:STDOUT: ret void, !dbg !12
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// CHECK:STDOUT: }
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// CHECK:STDOUT:
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// CHECK:STDOUT: attributes #0 = { nounwind }
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// CHECK:STDOUT:
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// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
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// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
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// CHECK:STDOUT:
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// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
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// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
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// CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
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// CHECK:STDOUT: !3 = !DIFile(filename: "method.carbon", directory: "")
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// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !8)
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// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
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// CHECK:STDOUT: !6 = !{null, !7}
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// CHECK:STDOUT: !7 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 8)
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// CHECK:STDOUT: !8 = !{!9}
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// CHECK:STDOUT: !9 = !DILocalVariable(arg: 1, scope: !4, type: !7)
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// CHECK:STDOUT: !10 = !DILocation(line: 21, column: 16, scope: !4)
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// CHECK:STDOUT: !11 = !DILocation(line: 22, column: 3, scope: !4)
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// CHECK:STDOUT: !12 = !DILocation(line: 20, column: 1, scope: !4)
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