This adds two related changes to HLSL debug info support in the SPIR-V
backend. It's a first small step towards the plan I described in
https://discourse.llvm.org/t/hlsl-spirv-nsdi-debug-info-support-for-clang-dxc/90149.
## Tag HLSL shaders with `DW_LANG_HLSL` in the front-end
`GetSourceLanguage()` in `clang/lib/CodeGen/CGDebugInfo.cpp` checked
`LO.CPlusPlus` before `LO.HLSL`. Since HLSL is compiled as C++, the HLSL
check was never reached. Shaders compiled with `-g` were tagged with
`DW_LANG_C_plus_plus_14` instead of `DW_LANG_HLSL`. The NSDI pass
already had the correct mapping for `DW_LANG_HLSL` but it was never
triggered.
This fixes#136929 and #136995.
## Make `SPIRVEmitNonSemanticDI` activate automatically when `-g` is
used
`SPIRVPassConfig::addPreEmitPass()` only scheduled
`SPIRVEmitNonSemanticDI` when `--spv-emit-nonsemantic-debug-info` was
set or the target vendor was AMD. Passing `-g` to clang had no effect on
the SPIR-V backend pass.
The pass is now added unconditionally and self-activates by checking for
`llvm.dbg.cu` in the module. When no debug metadata is present it exits
early with no effect. This avoids the need to inspect module metadata at
pass-configuration time, which is not reliably available.
`--spv-emit-nonsemantic-debug-info` is now a deprecated synonym for
`-g`.
The alternative to the unconditional pass approach is to check at
pass-configuration time whether the module was compiled with debug info
(e.g. via `TargetOptions::DebugInfoForProfiling` or a similar flag
forwarded from the driver). I went with the unconditional approach
because it is simpler and the pass is cheap to enter and exit when no
`llvm.dbg.cu` is present.
I'm not sure whether adding a pass unconditionally is acceptable. Does
this sound reasonable, or would it be better to implement the
flag-forwarding approach?
Changes to tests:
- `clang/test/CodeGenHLSL/` (new): verifies that `-g` on an HLSL SPIR-V
target produces `DebugCompilationUnit` with language code 5
(`DW_LANG_HLSL`).
-
`llvm/test/CodeGen/SPIRV/debug-info/hlsl-debug-info-auto-activation.ll`
(new): verifies that a module with `llvm.dbg.cu` and `DW_LANG_HLSL`
produces `DebugCompilationUnit` without
`--spv-emit-nonsemantic-debug-info`.
- Existing `debug-compilation-unit.ll`, `debug-type-basic.ll`,
`debug-type-pointer.ll`: updated to verify NSDI is emitted whenever
debug metadata is present.
- `llc-pipeline.ll`: updated to reflect that `SPIRVEmitNonSemanticDI` is
now always in the pipeline.
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Co-authored-by: Eric Christopher <echristo@gmail.com>
85049fc357