[debuginfo] generate debug info with asm+.file

[bcain]

Summary

For assembly input files, generate debug info even when the .file
directive is present, provided it does not include a file-number
argument.

[bcain]

Comments:

llvm/lib/MC/MCParser/AsmParser.cpp

3354–3361

This code block is the interesting part moreso than the if/else.

Before r328208, an effect similar to this was in the else clause (FileNumber != 1).

[probinson]

The indentation in the test looks a little odd. Please verify there are no hard tabs.
Otherwise LGTM.

Please cite the PR number in the commit message, when you push this.

[bcain]

• Changed indentation for nop
• Added PR number to summary

[bcain]

In D51315#1214857, @probinson wrote:

The indentation in the test looks a little odd. Please verify there are no hard tabs.
Otherwise LGTM.

Please cite the PR number in the commit message, when you push this.

There's no hard tabs. The only indentation oddness that I identified was the 4-space indentation for nop versus 8-space for the .file directive. Corrected nop to match the .file.

[probinson]

Awesome thanks!

llvm/lib/MC/MCParser/AsmParser.cpp

if (Keyword == "md5") {
                 "unexpected token in '.file' directive") ||
           parseEscapedString(SourceString))
         return true;
     } else {
       return TokError("unexpected token in '.file' directive");
     }
   }
 
+  if (FileNumber == -1)
+    getStreamer().EmitFileDirective(Filename);
+  else {
     // In case there is a -g option as well as debug info from directive .file,
     // we turn off the -g option, directly use the existing debug info instead.
     // Also reset any implicit ".file 0" for the assembler source.
     if (Ctx.getGenDwarfForAssembly()) {
       Ctx.getMCDwarfLineTable(0).resetRootFile();
       Ctx.setGenDwarfForAssembly(false);
     }
 
-  if (FileNumber == -1)
-    getStreamer().EmitFileDirective(Filename);
-  else {
     MD5::MD5Result *CKMem = nullptr;
     if (HasMD5) {
       CKMem = (MD5::MD5Result *)Ctx.allocate(sizeof(MD5::MD5Result), 1);
       for (unsigned i = 0; i != 8; ++i) {
         CKMem->Bytes[i] = uint8_t(MD5Hi >> ((7 - i) * 8));
         CKMem->Bytes[i + 8] = uint8_t(MD5Lo >> ((7 - i) * 8));
       }
     }

llvm/test/MC/AsmParser/directive_file-3.s

+// RUN: llvm-mc -g -triple i386-unknown-unknown  %s | FileCheck -check-prefix=CHECK-DEFAULT %s
+// RUN: llvm-mc -g -triple i386-unknown-unknown %s -filetype=obj | obj2yaml | FileCheck -check-prefix=CHECK-DEBUG %s
+
+// Test for Bug 38695
+// This testcase has a single function and a .file directive
+// without the [file-num] argument.  When compiled with -g,
+// this testcase will not report error, and generate new
+// debug info.
+
+        .file "hello"
+.text
+
+f1:
+    nop
+.size f1, .-f1
+
+// CHECK-DEFAULT: .file "hello"
+
+// CHECK-DEBUG:  Sections:
+// CHECK-DEBUG:  - Name:            .text
+// CHECK-DEBUG:  - Name:            .debug_info
+// CHECK-DEBUG:  - Name:            .rel.debug_info
+// CHECK-DEBUG:    Info:            .debug_info
+// CHECK-DEBUG:  Symbols: