md.texi: Describe the use of match_tests in attribute tests.

gcc/
	* doc/md.texi: Describe the use of match_tests in attribute tests.
	* rtl.def (MATCH_TEST): Update commentary.
	* genattrtab.c (attr_copy_rtx, check_attr_test, clear_struct_flag)
	(write_test_expr, walk_attr_value): Handle MATCH_TEST.

From-SVN: r178388

gcc/ChangeLog

 2011-08-31  Richard Sandiford  <rdsandiford@googlemail.com>
 
+	* doc/md.texi: Describe the use of match_tests in attribute tests.
+	* rtl.def (MATCH_TEST): Update commentary.
+	* genattrtab.c (attr_copy_rtx, check_attr_test, clear_struct_flag)
+	(write_test_expr, walk_attr_value): Handle MATCH_TEST.
+
+2011-08-31  Richard Sandiford  <rdsandiford@googlemail.com>
+
 	* genattrtab.c (attr_rtx_1): Hash SYMBOL_REFs.
 	(attr_string): Use copy_md_ptr_loc.
 

gcc/doc/md.texi

@@ -7045,6 +7045,30 @@ string).
 
 The @var{constraints} operand is ignored and should be the null string.
 
+@cindex @code{match_test} and attributes
+@item (match_test @var{c-expr})
+The test is true if C expression @var{c-expr} is true.  In non-constant
+attributes, @var{c-expr} has access to the following variables:
+
+@table @var
+@item insn
+The rtl instruction under test.
+@item which_alternative
+The @code{define_insn} alternative that @var{insn} matches.
+@xref{Output Statement}.
+@item operands
+An array of @var{insn}'s rtl operands.
+@end table
+
+@var{c-expr} behaves like the condition in a C @code{if} statement,
+so there is no need to explicitly convert the expression into a boolean
+0 or 1 value.  For example, the following two tests are equivalent:
+
+@smallexample
+(match_test "x & 2")
+(match_test "(x & 2) != 0")
+@end smallexample
+
 @cindex @code{le} and attributes
 @cindex @code{leu} and attributes
 @cindex @code{lt} and attributes

gcc/genattrtab.c

@@ -658,6 +658,7 @@ attr_copy_rtx (rtx orig)
     case CONST_DOUBLE:
     case CONST_VECTOR:
     case SYMBOL_REF:
+    case MATCH_TEST:
     case CODE_LABEL:
     case PC:
     case CC0:
@@ -841,6 +842,11 @@ check_attr_test (rtx exp, int is_const, int lineno)
       XEXP (exp, 0) = check_attr_test (XEXP (exp, 0), is_const, lineno);
       break;
 
+    case MATCH_TEST:
+      exp = attr_rtx (MATCH_TEST, XSTR (exp, 0));
+      ATTR_IND_SIMPLIFIED_P (exp) = 1;
+      break;
+
     case MATCH_OPERAND:
       if (is_const)
 	fatal ("RTL operator \"%s\" not valid in constant attribute test",
@@ -2907,6 +2913,7 @@ clear_struct_flag (rtx x)
     case CONST_INT:
     case CONST_DOUBLE:
     case CONST_VECTOR:
+    case MATCH_TEST:
     case SYMBOL_REF:
     case CODE_LABEL:
     case PC:
@@ -3571,6 +3578,12 @@ write_test_expr (rtx exp, unsigned int attrs_cached, int flags)
       printf (HOST_WIDE_INT_PRINT_DEC, XWINT (exp, 0));
       break;
 
+    case MATCH_TEST:
+      print_c_condition (XSTR (exp, 0));
+      if (flags & FLG_BITWISE)
+	printf (" != 0");
+      break;
+
     /* A random C expression.  */
     case SYMBOL_REF:
       print_c_condition (XSTR (exp, 0));
@@ -3765,6 +3778,7 @@ walk_attr_value (rtx exp)
       must_extract = 1;
       return;
 
+    case MATCH_TEST:
     case EQ_ATTR_ALT:
       must_extract = must_constrain = 1;
       break;

gcc/rtl.def

@@ -819,9 +819,8 @@ DEF_RTL_EXPR(MATCH_PAR_DUP, "match_par_dup", "iE", RTX_MATCH)
    the result of the one before it.  */
 DEF_RTL_EXPR(MATCH_CODE, "match_code", "ss", RTX_MATCH)
 
-/* Appears only in define_predicate/define_special_predicate
-    expressions.  The argument is a C expression to be injected at this
-    point in the predicate formula.  */
+/* Used to inject a C conditional expression into an .md file.  It can
+   appear in a predicate definition or an attribute expression.  */
 DEF_RTL_EXPR(MATCH_TEST, "match_test", "s", RTX_MATCH)
 
 /* Insn (and related) definitions.  */