x86 codegen: don't generate location comments

The following source snippet 'module A where x */* y = 42'
when being compiled with '-g' option emits syntactically
invalid comment for GNU as:

    .text
        .align 8
        .loc 1 3 1 /* */* */

Fixed by not emitting comments at all. We already suppress
all asm comments in 'X86/Ppr.hs'.

Signed-off-by: Sergei Trofimovich <siarheit@google.com>

Test Plan: added test and check it works

Reviewers: scpmw, simonmar, austin, bgamari

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1386

GHC Trac Issues: #10667

compiler/nativeGen/X86/Ppr.hs

@@ -506,9 +506,8 @@ pprInstr (COMMENT _) = empty -- nuke 'em
 pprInstr (COMMENT s) = ptext (sLit "# ") <> ftext s
 -}
 
-pprInstr (LOCATION file line col name)
-   = ptext (sLit "\t.loc ") <> ppr file <+> ppr line <+> ppr col <>
-     ptext (sLit " /* ") <> text name <> ptext (sLit " */")
+pprInstr (LOCATION file line col _name)
+   = ptext (sLit "\t.loc ") <> ppr file <+> ppr line <+> ppr col
 
 pprInstr (DELTA d)
    = pprInstr (COMMENT (mkFastString ("\tdelta = " ++ show d)))

testsuite/tests/codeGen/should_compile/T10667.hs

+module A where
+
+-- when used with '-g' debug generation option
+-- '*/*' leaked into a /* comment */ and broke
+-- GNU as.
+x */* y = 42

testsuite/tests/codeGen/should_compile/all.T

@@ -31,3 +31,4 @@ test('debug', extra_clean(['debug.cmm']),
      ['$MAKE -s --no-print-directory debug'])
 test('T9964', normal, compile, ['-O'])
 test('T10518', [cmm_src], compile, [''])
+test('T10667', normal, compile, ['-g'])