[NVPTX] Do not emit .target debug if only line tables are requested

[superbobry]

According to *, only the deprecated @@DWARF directives require setting .target debug.

[llvmbot]

@llvm/pr-subscribers-debuginfo

@llvm/pr-subscribers-backend-nvptx

Author: Sergei Lebedev (superbobry)

Changes

According to *, only the deprecated @@<!-- -->DWARF directives require setting .target debug.

---

Full diff: https://github.com/llvm/llvm-project/pull/140146.diff

2 Files Affected:

• (modified) llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp (+1-1)
• (modified) llvm/test/DebugInfo/NVPTX/debug-file-loc.ll (+1-1)

diff --git a/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp b/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
index 0e5207cf9b04c..5b5d72e310ce2 100644
--- a/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
@@ -745,8 +745,8 @@ void NVPTXAsmPrinter::emitHeader(Module &M, raw_ostream &O,
     switch(CU->getEmissionKind()) {
     case DICompileUnit::NoDebug:
     case DICompileUnit::DebugDirectivesOnly:
-      break;
     case DICompileUnit::LineTablesOnly:
+      break;
     case DICompileUnit::FullDebug:
       HasFullDebugInfo = true;
       break;
diff --git a/llvm/test/DebugInfo/NVPTX/debug-file-loc.ll b/llvm/test/DebugInfo/NVPTX/debug-file-loc.ll
index 9d1d3506a3f19..258f8e79ad63a 100644
--- a/llvm/test/DebugInfo/NVPTX/debug-file-loc.ll
+++ b/llvm/test/DebugInfo/NVPTX/debug-file-loc.ll
@@ -9,7 +9,7 @@
 ;__device__ void bar() {}
 ;}
 
-; CHECK: .target sm_{{[0-9]+}}, debug
+; CHECK: .target sm_{{[0-9]+}}
 
 ; CHECK: .visible .func foo()
 ; CHECK: .loc [[FOO:[0-9]+]] 1 31

[superbobry]

PTX ISA is somewhat ambiguous in that section, but empirically ptxas does accept PTX with .section directives without .target debug.

[Artem-B]

@dwblaikie Do I understand it correctly that LineTablesOnly only implies that debug info will be limited to line info only, but it does not say anything about the format of that info. I.e. that it could be either done via debug directives or via DWARF.

If that's the case, then this change is wrong, and the current code is correct.

[dwblaikie]

LineTablesOnly unfortunately means /almost/ line tables only - it actually means line tables, /and/ enough of .debug_info to describe inlining.

The DebugDirectivesOnly is means /really/ only the debug directives that generate only the line table (.debug_line (and in DWARFv5, .debug_line_str)).