Add source information to -fverbose-asm

gcc/ChangeLog:
	* doc/invoke.texi (fverbose-asm): Note that source code lines
	are emitted, and provide an example.
	* final.c (asm_show_source): New function.
	(final_scan_insn): Call asm_show_source.

From-SVN: r239604

gcc/ChangeLog

@@ -1,3 +1,10 @@
+2016-08-18  David Malcolm  <dmalcolm@redhat.com>
+
+	* doc/invoke.texi (fverbose-asm): Note that source code lines
+	are emitted, and provide an example.
+	* final.c (asm_show_source): New function.
+	(final_scan_insn): Call asm_show_source.
+
 2016-08-18  David Malcolm  <dmalcolm@redhat.com>
 
 	* diagnostic-show-locus.c (colorizer::colorizer): Replace diagnostic

gcc/doc/invoke.texi

@@ -11426,6 +11426,89 @@ debugging the compiler itself).
 extra information to be omitted and is useful when comparing two assembler
 files.
 
+The added comments include:
+
+@itemize @bullet
+
+@item
+information on the compiler version and command-line options,
+
+@item
+the source code lines associated with the assembly instructions,
+in the form FILENAME:LINENUMBER:CONTENT OF LINE,
+
+@item
+hints on which high-level expressions correspond to
+the various assembly instruction operands.
+
+@end itemize
+
+For example, given this C source file:
+
+@smallexample
+int test (int n)
+@{
+  int i;
+  int total = 0;
+
+  for (i = 0; i < n; i++)
+    total += i * i;
+
+  return total;
+@}
+@end smallexample
+
+compiling to (x86_64) assembly via @option{-S} and emitting the result
+direct to stdout via @option{-o} @option{-}
+
+@smallexample
+gcc -S test.c -fverbose-asm -Os -o -
+@end smallexample
+
+gives output similar to this:
+
+@smallexample
+	.file	"test.c"
+# GNU C11 (GCC) version 7.0.0 20160809 (experimental) (x86_64-pc-linux-gnu)
+  [...snip...]
+# options passed:
+  [...snip...]
+
+	.text
+	.globl	test
+	.type	test, @@function
+test:
+.LFB0:
+	.cfi_startproc
+# test.c:4:   int total = 0;
+	xorl	%eax, %eax	# <retval>
+# test.c:6:   for (i = 0; i < n; i++)
+	xorl	%edx, %edx	# i
+.L2:
+# test.c:6:   for (i = 0; i < n; i++)
+	cmpl	%edi, %edx	# n, i
+	jge	.L5	#,
+# test.c:7:     total += i * i;
+	movl	%edx, %ecx	# i, tmp92
+	imull	%edx, %ecx	# i, tmp92
+# test.c:6:   for (i = 0; i < n; i++)
+	incl	%edx	# i
+# test.c:7:     total += i * i;
+	addl	%ecx, %eax	# tmp92, <retval>
+	jmp	.L2	#
+.L5:
+# test.c:10: @}
+	ret
+	.cfi_endproc
+.LFE0:
+	.size	test, .-test
+	.ident	"GCC: (GNU) 7.0.0 20160809 (experimental)"
+	.section	.note.GNU-stack,"",@@progbits
+@end smallexample
+
+The comments are intended for humans rather than machines and hence the
+precise format of the comments is subject to change.
+
 @item -frecord-gcc-switches
 @opindex frecord-gcc-switches
 This switch causes the command line used to invoke the

gcc/final.c

@@ -2140,6 +2140,26 @@ call_from_call_insn (rtx_call_insn *insn)
   return x;
 }
 
+/* Print a comment into the asm showing FILENAME, LINENUM, and the
+   corresponding source line, if available.  */
+
+static void
+asm_show_source (const char *filename, int linenum)
+{
+  if (!filename)
+    return;
+
+  int line_size;
+  const char *line = location_get_source_line (filename, linenum, &line_size);
+  if (!line)
+    return;
+
+  fprintf (asm_out_file, "%s %s:%i: ", ASM_COMMENT_START, filename, linenum);
+  /* "line" is not 0-terminated, so we must use line_size.  */
+  fwrite (line, 1, line_size, asm_out_file);
+  fputc ('\n', asm_out_file);
+}
+
 /* The final scan for one insn, INSN.
    Args are same as in `final', except that INSN
    is the insn being scanned.
@@ -2563,8 +2583,12 @@ final_scan_insn (rtx_insn *insn, FILE *file, int optimize_p ATTRIBUTE_UNUSED,
 	   note in a row.  */
 	if (!DECL_IGNORED_P (current_function_decl)
 	    && notice_source_line (insn, &is_stmt))
-	  (*debug_hooks->source_line) (last_linenum, last_filename,
-				       last_discriminator, is_stmt);
+	  {
+	    if (flag_verbose_asm)
+	      asm_show_source (last_filename, last_linenum);
+	    (*debug_hooks->source_line) (last_linenum, last_filename,
+					 last_discriminator, is_stmt);
+	  }
 
 	if (GET_CODE (body) == PARALLEL
 	    && GET_CODE (XVECEXP (body, 0, 0)) == ASM_INPUT)

gcc/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2016-08-18  David Malcolm  <dmalcolm@redhat.com>
+
+	* gcc.dg/verbose-asm-2.c: New test case.
+
 2016-08-18  David Malcolm  <dmalcolm@redhat.com>
 
 	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c

gcc/testsuite/gcc.dg/verbose-asm-2.c

@@ -0,0 +1,15 @@
+/* Ensure that the -fverbose-asm leads to source code information in the generated asm.  */
+/* { dg-options "-fverbose-asm" } */
+
+int test (int n)
+{
+  int i;
+  int total = 0;
+
+  for (i = 0; i < n; i++)
+    total += i * i;
+
+  return total;
+}
+
+/* { dg-final { scan-assembler "total = 0" } } */