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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>
78 lines
4.5 KiB
Plaintext
78 lines
4.5 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/primitives.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/if_expr/empty_block.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/if_expr/empty_block.carbon
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fn Select(b: bool, c: bool, d: bool) -> i32 {
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return if b then if c then 1 as i32 else 2 else if d then 3 as i32 else 4;
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}
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// CHECK:STDOUT: ; ModuleID = 'empty_block.carbon'
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// CHECK:STDOUT: source_filename = "empty_block.carbon"
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// CHECK:STDOUT:
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// CHECK:STDOUT: ; Function Attrs: nounwind
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// CHECK:STDOUT: define i32 @_CSelect.Main(i1 %b, i1 %c, i1 %d) #0 !dbg !4 {
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// CHECK:STDOUT: entry:
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// CHECK:STDOUT: br i1 %b, label %if.expr.then.loc14_10, label %if.expr.else.loc14_10, !dbg !13
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.then.loc14_10: ; preds = %entry
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// CHECK:STDOUT: br i1 %c, label %if.expr.then.loc14_20, label %if.expr.else.loc14_20, !dbg !14
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.then.loc14_20: ; preds = %if.expr.then.loc14_10
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// CHECK:STDOUT: br label %if.expr.result.loc14_20, !dbg !14
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.else.loc14_20: ; preds = %if.expr.then.loc14_10
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// CHECK:STDOUT: br label %if.expr.result.loc14_20, !dbg !14
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.result.loc14_20: ; preds = %if.expr.else.loc14_20, %if.expr.then.loc14_20
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// CHECK:STDOUT: %0 = phi i32 [ 1, %if.expr.then.loc14_20 ], [ 2, %if.expr.else.loc14_20 ]
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// CHECK:STDOUT: br label %if.expr.result.loc14_10, !dbg !13
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.else.loc14_10: ; preds = %entry
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// CHECK:STDOUT: br i1 %d, label %if.expr.then.loc14_51, label %if.expr.else.loc14_51, !dbg !15
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.then.loc14_51: ; preds = %if.expr.else.loc14_10
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// CHECK:STDOUT: br label %if.expr.result.loc14_51, !dbg !15
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.else.loc14_51: ; preds = %if.expr.else.loc14_10
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// CHECK:STDOUT: br label %if.expr.result.loc14_51, !dbg !15
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.result.loc14_51: ; preds = %if.expr.else.loc14_51, %if.expr.then.loc14_51
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// CHECK:STDOUT: %1 = phi i32 [ 3, %if.expr.then.loc14_51 ], [ 4, %if.expr.else.loc14_51 ]
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// CHECK:STDOUT: br label %if.expr.result.loc14_10, !dbg !13
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// CHECK:STDOUT:
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// CHECK:STDOUT: if.expr.result.loc14_10: ; preds = %if.expr.result.loc14_51, %if.expr.result.loc14_20
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// CHECK:STDOUT: %2 = phi i32 [ %0, %if.expr.result.loc14_20 ], [ %1, %if.expr.result.loc14_51 ]
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// CHECK:STDOUT: ret i32 %2, !dbg !16
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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: "empty_block.carbon", directory: "")
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// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Select", linkageName: "_CSelect.Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !9)
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// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
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// CHECK:STDOUT: !6 = !{!7, !8, !8, !8}
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// CHECK:STDOUT: !7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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// CHECK:STDOUT: !8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 8)
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// CHECK:STDOUT: !9 = !{!10, !11, !12}
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// CHECK:STDOUT: !10 = !DILocalVariable(arg: 1, scope: !4, type: !8)
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// CHECK:STDOUT: !11 = !DILocalVariable(arg: 2, scope: !4, type: !8)
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// CHECK:STDOUT: !12 = !DILocalVariable(arg: 3, scope: !4, type: !8)
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// CHECK:STDOUT: !13 = !DILocation(line: 14, column: 10, scope: !4)
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// CHECK:STDOUT: !14 = !DILocation(line: 14, column: 20, scope: !4)
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// CHECK:STDOUT: !15 = !DILocation(line: 14, column: 51, scope: !4)
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// CHECK:STDOUT: !16 = !DILocation(line: 14, column: 3, scope: !4)
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