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a179bd461b4a07bf2defe91e68f1bb9edfa60551
carbon-lang/toolchain/lower/testdata/function/generic/call_impl_function.carbon
T
David BlaikieandDana Jansens a179bd461b Start plumbing through debug info type information with function parameters/return value (#6410) 
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>
2025-11-25 23:25:09 +00:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/int.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/function/generic/call_impl_function.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/generic/call_impl_function.carbon
interface SomeInterface(T:! type) {
fn F(x: T) -> T;
}
class SomeParam {}
class ImplsSomeInterface {}
impl ImplsSomeInterface as SomeInterface(i32) {
fn F(x: i32) -> i32 {
return -x;
}
}
// TODO: This asserts with "Mangled name collision".
// impl ImplsSomeInterface as SomeInterface(SomeParam) {
// fn F(x: SomeParam) -> SomeParam {
// return {};
// }
// }
fn CallGenericMethod(T:! type, U:! SomeInterface(T), x: T) -> T {
return U.F(x);
}
fn G() {
CallGenericMethod(i32, ImplsSomeInterface, 10);
// TODO: Fix above
// CallGenericMethod(SomeParam, ImplsSomeInterface, {});
}
// CHECK:STDOUT: ; ModuleID = 'call_impl_function.carbon'
// CHECK:STDOUT: source_filename = "call_impl_function.carbon"
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define i32 @"_CF.ImplsSomeInterface.Main:SomeInterface.Main"(i32 %x) #0 !dbg !4 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %Int.as.Negate.impl.Op.call = sub i32 0, %x, !dbg !10
// CHECK:STDOUT: ret i32 %Int.as.Negate.impl.Op.call, !dbg !11
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define void @_CG.Main() #0 !dbg !12 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %CallGenericMethod.call = call i32 @_CCallGenericMethod.Main.dc54e41cb8a9bf68(i32 10), !dbg !15
// CHECK:STDOUT: ret void, !dbg !16
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define linkonce_odr i32 @_CCallGenericMethod.Main.dc54e41cb8a9bf68(i32 %x) #0 !dbg !17 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %.loc36_15 = call i32 @"_CF.ImplsSomeInterface.Main:SomeInterface.Main"(i32 %x), !dbg !20
// CHECK:STDOUT: ret i32 %.loc36_15, !dbg !21
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: attributes #0 = { nounwind }
// CHECK:STDOUT:
// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
// CHECK:STDOUT:
// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
// CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
// CHECK:STDOUT: !3 = !DIFile(filename: "call_impl_function.carbon", directory: "")
// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.ImplsSomeInterface.Main:SomeInterface.Main", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !8)
// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
// CHECK:STDOUT: !6 = !{!7, !7}
// CHECK:STDOUT: !7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
// CHECK:STDOUT: !8 = !{!9}
// CHECK:STDOUT: !9 = !DILocalVariable(arg: 1, scope: !4, type: !7)
// CHECK:STDOUT: !10 = !DILocation(line: 23, column: 12, scope: !4)
// CHECK:STDOUT: !11 = !DILocation(line: 23, column: 5, scope: !4)
// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main", scope: null, file: !3, line: 39, type: !13, spFlags: DISPFlagDefinition, unit: !2)
// CHECK:STDOUT: !13 = !DISubroutineType(types: !14)
// CHECK:STDOUT: !14 = !{null}
// CHECK:STDOUT: !15 = !DILocation(line: 40, column: 3, scope: !12)
// CHECK:STDOUT: !16 = !DILocation(line: 39, column: 1, scope: !12)
// CHECK:STDOUT: !17 = distinct !DISubprogram(name: "CallGenericMethod", linkageName: "_CCallGenericMethod.Main.dc54e41cb8a9bf68", scope: null, file: !3, line: 35, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !18)
// CHECK:STDOUT: !18 = !{!19}
// CHECK:STDOUT: !19 = !DILocalVariable(arg: 1, scope: !17, type: !7)
// CHECK:STDOUT: !20 = !DILocation(line: 36, column: 10, scope: !17)
// CHECK:STDOUT: !21 = !DILocation(line: 36, column: 3, scope: !17)
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