i386.md: Global update to use new string syntax where it will improve readability.

	* config/i386/i386.md: Global update to use new string syntax
	where it will improve readability.  Warning fixes:
	(*truncdfsf2_2): Abort if which_alternative is not 0 or 1.
	(*adddi_1_rex64, *adddi_2_rex64, *adddi_3_rex64,
	*adddi_4_rex64, *adddi_5_rex64): Cast 1 to unsigned int.

	* read-rtl.c: Syntactic sugar for C embedded in strings in
	machine descriptions.
	(read_string): Break inner loop into separate function.  Takes
	an int.  Dispatch to read_quoted_string or read_braced_string
	as appropriate.  Automatically insert a leading star on braced
	strings if STAR_IF_BRACED is true.
	(read_quoted_string, read_braced_string): New functions.
	* doc/rtl.texi, doc/md.texi: Document new syntax.  Update
	examples to match.

	* rtl.c: Split RTL reader (read_rtx, read_skip_spaces,
	traverse_md_constants, fatal_with_file_and_line,
	fatal_expected_char, read_name, read_string, def_hash,
	def_name_eq_p, read_constants, and related data) to its own
	file.  Weed out now-unnecessary #includes.
	* read-rtl.c: New file.
	* Makefile.in (HOST_RTL): Add read-rtl.o.
	(read-rtl.o): New rule.
	(rtl.o, $(HOST_PREFIX_1)rtl.o): Update dependencies.
	* doc/gcc.texi (Passes): Talk briefly about the support
	library used by genfoo.
	* doc/rtl.texi (Reading RTL): read_rtx is not available in the
	compiler itself.

From-SVN: r43646

3 files changed, 59 insertions, 22 deletions

diff --git a/gcc/doc/gcc.texi b/gcc/doc/gcc.texi
index be4773e..6601ab6 100644
--- a/gcc/doc/gcc.texi
+++ b/gcc/doc/gcc.texi
@@ -3724,6 +3724,10 @@ and @file{rtl.def}, and subroutines in file @file{rtl.c}.  The tools
 @code{gen*} also use these files to read and work with the machine
 description RTL@.
 
+@item
+All the tools that read the machine description use support routines
+found in @file{gensupport.c}, @file{errors.c}, and @file{read-rtl.c}.
+
 @findex genconfig
 @item
 Several passes refer to the header file @file{insn-config.h} which
diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index 15374c6..3d4d2b1 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -184,9 +184,26 @@ Here is an actual example of an instruction pattern, for the 68000/68020.
         (match_operand:SI 0 "general_operand" "rm"))]
   ""
   "*
-@{ if (TARGET_68020 || ! ADDRESS_REG_P (operands[0]))
+@{ 
+  if (TARGET_68020 || ! ADDRESS_REG_P (operands[0]))
     return \"tstl %0\";
-  return \"cmpl #0,%0\"; @}")
+  return \"cmpl #0,%0\"; 
+@}")
+@end example
+
+@noindent
+This can also be written using braced strings:
+
+@example
+(define_insn "tstsi"
+  [(set (cc0)
+        (match_operand:SI 0 "general_operand" "rm"))]
+  ""
+@{ 
+  if (TARGET_68020 || ! ADDRESS_REG_P (operands[0]))
+    return "tstl %0";
+  return "cmpl #0,%0"; 
+@})
 @end example
 
 This is an instruction that sets the condition codes based on the value of
@@ -620,6 +637,11 @@ template-string you want.  Most such templates use C string literals, which
 require doublequote characters to delimit them.  To include these
 doublequote characters in the string, prefix each one with @samp{\}.
 
+If the output control string is written as a brace block instead of a
+double-quoted string, it is automatically assumed to be C code.  In that
+case, it is not necessary to put in a leading asterisk, or to escape the
+doublequotes surrounding C string literals.
+
 The operands may be found in the array @code{operands}, whose C data type
 is @code{rtx []}.
 
@@ -656,10 +678,10 @@ a pattern could use @code{which_alternative} to choose between them:
   [(set (match_operand:SI 0 "general_operand" "=r,m")
         (const_int 0))]
   ""
-  "*
+  @{
   return (which_alternative == 0
-          ? \"clrreg %0\" : \"clrmem %0\");
-  ")
+          ? "clrreg %0" : "clrmem %0");
+  @})
 @end smallexample
 
 The example above, where the assembler code to generate was
@@ -3943,21 +3965,19 @@ Here is an example, taken from the 68000 machine description:
    (set (match_operand:DF 0 "register_operand" "=f")
         (match_operand:DF 1 "register_operand" "ad"))]
   "FP_REG_P (operands[0]) && ! FP_REG_P (operands[1])"
-  "*
 @{
   rtx xoperands[2];
   xoperands[1] = gen_rtx (REG, SImode, REGNO (operands[1]) + 1);
 #ifdef MOTOROLA
-  output_asm_insn (\"move.l %1,(sp)\", xoperands);
-  output_asm_insn (\"move.l %1,-(sp)\", operands);
-  return \"fmove.d (sp)+,%0\";
+  output_asm_insn ("move.l %1,(sp)", xoperands);
+  output_asm_insn ("move.l %1,-(sp)", operands);
+  return "fmove.d (sp)+,%0";
 #else
-  output_asm_insn (\"movel %1,sp@@\", xoperands);
-  output_asm_insn (\"movel %1,sp@@-\", operands);
-  return \"fmoved sp@@+,%0\";
+  output_asm_insn ("movel %1,sp@@", xoperands);
+  output_asm_insn ("movel %1,sp@@-", operands);
+  return "fmoved sp@@+,%0";
 #endif
-@}
-")
+@})
 @end smallexample
 
 @need 1000
@@ -4656,11 +4676,10 @@ as follows:
   [(set (pc)
         (label_ref (match_operand 0 "" "")))]
   ""
-  "*
 @{
    return (get_attr_length (insn) == 4
-           ? \"b %l0\" : \"l r15,=a(%l0); br r15\");
-@}"
+           ? "b %l0" : "l r15,=a(%l0); br r15");
+@}
   [(set (attr "length") (if_then_else (lt (match_dup 0) (const_int 4096))
                                       (const_int 4)
                                       (const_int 6)))])
diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi
index dbd3691..618322a 100644
--- a/gcc/doc/rtl.texi
+++ b/gcc/doc/rtl.texi
@@ -70,6 +70,21 @@ pointers instead of strings are valid.  Within RTL code, strings are most
 commonly found inside @code{symbol_ref} expressions, but they appear in
 other contexts in the RTL expressions that make up machine descriptions.
 
+In a machine description, strings are normally written with double
+quotes, as you would in C.  However, strings in machine descriptions may
+extend over many lines, which is invalid C, and adjacent string
+constants are not concatenated as they are in C.  Any string constant
+may be surrounded with a single set of parentheses.  Sometimes this
+makes the machine description easier to read.
+
+There is also a special syntax for strings, which can be useful when C
+code is embedded in a machine description.  Wherever a string can
+appear, it is also valid to write a C-style brace block.  The entire
+brace block, including the outermost pair of braces, is considered to be
+the string constant.  Double quote characters inside the braces are not
+special.  Therefore, if you write string constants in the C code, you
+need not escape each quote character with a backslash.
+
 A vector contains an arbitrary number of pointers to expressions.  The
 number of elements in the vector is explicitly present in the vector.
 The written form of a vector consists of square brackets
@@ -3182,11 +3197,10 @@ combiner is finished with the insn.  This is done by calling
 @section Reading RTL
 
 To read an RTL object from a file, call @code{read_rtx}.  It takes one
-argument, a stdio stream, and returns a single RTL object.
-
-Reading RTL from a file is very slow.  This is not currently a
-problem since reading RTL occurs only as part of building the
-compiler.
+argument, a stdio stream, and returns a single RTL object.  This routine
+is defined in @file{read-rtl.c}.  It is not available in the compiler
+itself, only the various programs that generate the compiler back end
+from the machine description.
 
 People frequently have the idea of using RTL stored as text in a file as
 an interface between a language front end and the bulk of GCC@.  This