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[PATCH 1/8] asm qualifiers (PR55681)


PR55681 observes that currently only one qualifier is allowed for
inline asm, so that e.g. "volatile asm" is allowed, "const asm" is also
okay (with a warning), but "const volatile asm" gives an error.  Also
"goto" has to be last.

This patch changes things so that only "asm-qualifiers" are allowed,
that is "volatile" and "goto", in any combination, in any order, but
without repetitions.

2018-12-06  Segher Boessenkool  <segher@kernel.crashing.org>

	PR inline-asm/55681
	* doc/extend.texi (Basic Asm): Update grammar.
	(Extended Asm): Update grammar.

gcc/c/
	PR inline-asm/55681
	* c-parser.c (c_parser_asm_statement): Update grammar.  Allow any
	combination of volatile and goto, in any order, without repetitions.

gcc/cp/
	PR inline-asm/55681
	* parser.c (cp_parser_asm_definition): Update grammar.  Allow any
	combination of volatile and goto, in any order, without repetitions.

gcc/testsuite/
	PR inline-asm/55681
	* gcc.dg/asm-qual-1.c: Test that "const" and "restrict" are refused.
	* gcc.dg/asm-qual-2.c: New test, test that asm-qualifiers are allowed
	in any order, but that duplicates are not allowed.
---
 gcc/c/c-parser.c                  | 74 +++++++++++++++++++++----------------
 gcc/cp/parser.c                   | 77 ++++++++++++++++++++++++++-------------
 gcc/doc/extend.texi               |  8 ++--
 gcc/testsuite/gcc.dg/asm-qual-1.c | 10 +++--
 gcc/testsuite/gcc.dg/asm-qual-2.c | 21 +++++++++++
 5 files changed, 127 insertions(+), 63 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/asm-qual-2.c

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 4772086..7ec53b3 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -6261,60 +6261,72 @@ c_parser_for_statement (c_parser *parser, bool ivdep, unsigned short unroll,
 }
 
 /* Parse an asm statement, a GNU extension.  This is a full-blown asm
-   statement with inputs, outputs, clobbers, and volatile tag
+   statement with inputs, outputs, clobbers, and volatile and goto tag
    allowed.
 
+   asm-qualifier:
+     volatile
+     goto
+
+   asm-qualifier-list:
+     asm-qualifier-list asm-qualifier
+     asm-qualifier
+
    asm-statement:
-     asm type-qualifier[opt] ( asm-argument ) ;
-     asm type-qualifier[opt] goto ( asm-goto-argument ) ;
+     asm asm-qualifier-list[opt] ( asm-argument ) ;
 
    asm-argument:
      asm-string-literal
      asm-string-literal : asm-operands[opt]
      asm-string-literal : asm-operands[opt] : asm-operands[opt]
-     asm-string-literal : asm-operands[opt] : asm-operands[opt] : asm-clobbers[opt]
-
-   asm-goto-argument:
+     asm-string-literal : asm-operands[opt] : asm-operands[opt] \
+       : asm-clobbers[opt]
      asm-string-literal : : asm-operands[opt] : asm-clobbers[opt] \
        : asm-goto-operands
 
-   Qualifiers other than volatile are accepted in the syntax but
-   warned for.  */
+   The form with asm-goto-operands is valid if and only if the
+   asm-qualifier-list contains goto, and is the only allowed form in that case.
+   Duplicate asm-qualifiers are not allowed.  */
 
 static tree
 c_parser_asm_statement (c_parser *parser)
 {
   tree quals, str, outputs, inputs, clobbers, labels, ret;
-  bool simple, is_goto;
+  bool simple, is_volatile, is_goto;
   location_t asm_loc = c_parser_peek_token (parser)->location;
   int section, nsections;
 
   gcc_assert (c_parser_next_token_is_keyword (parser, RID_ASM));
   c_parser_consume_token (parser);
-  if (c_parser_next_token_is_keyword (parser, RID_VOLATILE))
-    {
-      quals = c_parser_peek_token (parser)->value;
-      c_parser_consume_token (parser);
-    }
-  else if (c_parser_next_token_is_keyword (parser, RID_CONST)
-	   || c_parser_next_token_is_keyword (parser, RID_RESTRICT))
-    {
-      warning_at (c_parser_peek_token (parser)->location,
-		  0,
-		  "%E qualifier ignored on asm",
-		  c_parser_peek_token (parser)->value);
-      quals = NULL_TREE;
-      c_parser_consume_token (parser);
-    }
-  else
-    quals = NULL_TREE;
 
+  quals = NULL_TREE;
+  is_volatile = false;
   is_goto = false;
-  if (c_parser_next_token_is_keyword (parser, RID_GOTO))
-    {
-      c_parser_consume_token (parser);
-      is_goto = true;
-    }
+  for (bool done = false; !done; )
+    switch (c_parser_peek_token (parser)->keyword)
+      {
+      case RID_VOLATILE:
+	if (!is_volatile)
+	  {
+	    is_volatile = true;
+	    quals = c_parser_peek_token (parser)->value;
+	    c_parser_consume_token (parser);
+	  }
+	else
+	  done = true;
+	break;
+      case RID_GOTO:
+	if (!is_goto)
+	  {
+	    is_goto = true;
+	    c_parser_consume_token (parser);
+	  }
+	else
+	  done = true;
+	break;
+      default:
+	done = true;
+      }
 
   /* ??? Follow the C++ parser rather than using the
      lex_untranslated_string kludge.  */
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 9907180..3bc5795 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -19067,22 +19067,34 @@ cp_parser_using_directive (cp_parser* parser)
 
 /* Parse an asm-definition.
 
+  asm-qualifier:
+    volatile
+    goto
+
+  asm-qualifier-list:
+    asm-qualifier
+    asm-qualifier-list asm-qualifier
+
    asm-definition:
      asm ( string-literal ) ;
 
    GNU Extension:
 
    asm-definition:
-     asm volatile [opt] ( string-literal ) ;
-     asm volatile [opt] ( string-literal : asm-operand-list [opt] ) ;
-     asm volatile [opt] ( string-literal : asm-operand-list [opt]
-			  : asm-operand-list [opt] ) ;
-     asm volatile [opt] ( string-literal : asm-operand-list [opt]
-			  : asm-operand-list [opt]
+     asm asm-qualifier-list [opt] ( string-literal ) ;
+     asm asm-qualifier-list [opt] ( string-literal : asm-operand-list [opt] ) ;
+     asm asm-qualifier-list [opt] ( string-literal : asm-operand-list [opt]
+				    : asm-operand-list [opt] ) ;
+     asm asm-qualifier-list [opt] ( string-literal : asm-operand-list [opt]
+				    : asm-operand-list [opt]
 			  : asm-clobber-list [opt] ) ;
-     asm volatile [opt] goto ( string-literal : : asm-operand-list [opt]
-			       : asm-clobber-list [opt]
-			       : asm-goto-list ) ;  */
+     asm asm-qualifier-list [opt] ( string-literal : : asm-operand-list [opt]
+				    : asm-clobber-list [opt]
+				    : asm-goto-list ) ;
+
+  The form with asm-goto-list is valid if and only if the asm-qualifier-list
+  contains goto, and is the only allowed form in that case.  No duplicates are
+  allowed in an asm-qualifier-list.  */
 
 static void
 cp_parser_asm_definition (cp_parser* parser)
@@ -19111,23 +19123,36 @@ cp_parser_asm_definition (cp_parser* parser)
     }
 
   /* See if the next token is `volatile'.  */
-  if (cp_parser_allow_gnu_extensions_p (parser)
-      && cp_lexer_next_token_is_keyword (parser->lexer, RID_VOLATILE))
-    {
-      /* Remember that we saw the `volatile' keyword.  */
-      volatile_p = true;
-      /* Consume the token.  */
-      cp_lexer_consume_token (parser->lexer);
-    }
-  if (cp_parser_allow_gnu_extensions_p (parser)
-      && parser->in_function_body
-      && cp_lexer_next_token_is_keyword (parser->lexer, RID_GOTO))
-    {
-      /* Remember that we saw the `goto' keyword.  */
-      goto_p = true;
-      /* Consume the token.  */
-      cp_lexer_consume_token (parser->lexer);
-    }
+  if (cp_parser_allow_gnu_extensions_p (parser))
+    for (bool done = false; !done ; )
+      switch (cp_lexer_peek_token (parser->lexer)->keyword)
+	{
+	case RID_VOLATILE:
+	  if (!volatile_p)
+	    {
+	      /* Remember that we saw the `volatile' keyword.  */
+	      volatile_p = true;
+	      /* Consume the token.  */
+	      cp_lexer_consume_token (parser->lexer);
+	    }
+	  else
+	    done = true;
+	  break;
+	case RID_GOTO:
+	  if (!goto_p && parser->in_function_body)
+	    {
+	      /* Remember that we saw the `goto' keyword.  */
+	      goto_p = true;
+	      /* Consume the token.  */
+	      cp_lexer_consume_token (parser->lexer);
+	    }
+	  else
+	    done = true;
+	  break;
+	default:
+	  done = true;
+	}
+
   /* Look for the opening `('.  */
   if (!cp_parser_require (parser, CPP_OPEN_PAREN, RT_OPEN_PAREN))
     return;
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index afde889..40b1989 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -8147,7 +8147,7 @@ for a C symbol, or to place a C variable in a specific register.
 A basic @code{asm} statement has the following syntax:
 
 @example
-asm @r{[} volatile @r{]} ( @var{AssemblerInstructions} )
+asm @var{asm-qualifiers} ( @var{AssemblerInstructions} )
 @end example
 
 The @code{asm} keyword is a GNU extension.
@@ -8275,17 +8275,19 @@ Extended @code{asm} syntax uses colons (@samp{:}) to delimit
 the operand parameters after the assembler template:
 
 @example
-asm @r{[}volatile@r{]} ( @var{AssemblerTemplate} 
+asm @var{asm-qualifiers} ( @var{AssemblerTemplate} 
                  : @var{OutputOperands} 
                  @r{[} : @var{InputOperands}
                  @r{[} : @var{Clobbers} @r{]} @r{]})
 
-asm @r{[}volatile@r{]} goto ( @var{AssemblerTemplate} 
+asm @var{asm-qualifiers} ( @var{AssemblerTemplate} 
                       : 
                       : @var{InputOperands}
                       : @var{Clobbers}
                       : @var{GotoLabels})
 @end example
+where in the last form, @var{asm-qualifiers} contains @code{goto} (and in the
+first form, not).
 
 The @code{asm} keyword is a GNU extension.
 When writing code that can be compiled with @option{-ansi} and the
diff --git a/gcc/testsuite/gcc.dg/asm-qual-1.c b/gcc/testsuite/gcc.dg/asm-qual-1.c
index 5ec9a29..cb37283 100644
--- a/gcc/testsuite/gcc.dg/asm-qual-1.c
+++ b/gcc/testsuite/gcc.dg/asm-qual-1.c
@@ -1,4 +1,4 @@
-/* Test that qualifiers other than volatile are ignored on asm.  */
+/* Test that qualifiers other than volatile are disallowed on asm.  */
 /* Origin: Joseph Myers <joseph@codesourcery.com> */
 /* { dg-do compile } */
 /* { dg-options "-std=gnu99" } */
@@ -7,6 +7,10 @@ void
 f (void)
 {
   asm volatile ("");
-  asm const (""); /* { dg-warning "const qualifier ignored on asm" } */
-  asm restrict (""); /* { dg-warning "restrict qualifier ignored on asm" } */
+
+  asm const (""); /* { dg-error {expected '\(' before 'const'} } */
+  /* { dg-error {expected identifier} {} {target *-*-*} .-1 } */
+
+  asm restrict (""); /* { dg-error {expected '\(' before 'restrict'} } */
+  /* { dg-error {expected identifier} {} {target *-*-*} .-1 } */
 }
diff --git a/gcc/testsuite/gcc.dg/asm-qual-2.c b/gcc/testsuite/gcc.dg/asm-qual-2.c
new file mode 100644
index 0000000..37df2ad
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/asm-qual-2.c
@@ -0,0 +1,21 @@
+/* Test that qualifiers on asm are allowed in any order.  */
+/* { dg-do compile } */
+/* { dg-options "-std=gnu99" } */
+
+void
+f (void)
+{
+  asm volatile goto ("" :::: lab);
+  asm goto volatile ("" :::: lab);
+
+  /* Duplicates are not allowed.  */
+  asm goto volatile volatile ("" :::: lab);  /* { dg-error "" } */
+  asm volatile goto volatile ("" :::: lab);  /* { dg-error "" } */
+  asm volatile volatile goto ("" :::: lab);  /* { dg-error "" } */
+  asm goto goto volatile ("" :::: lab);  /* { dg-error "" } */
+  asm goto volatile goto ("" :::: lab);  /* { dg-error "" } */
+  asm volatile goto goto ("" :::: lab);  /* { dg-error "" } */
+
+lab:
+  ;
+}
-- 
1.8.3.1


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