msp430.c (msp430_attr): Warn when the critical and interrupt function attributes are used together.

2018-12-29  Jozef Lawrynowicz  <jozef.l@mittosystems.com>

	gcc/ChangeLog:

	* config/msp430/msp430.c (msp430_attr): Warn when the critical and
	interrupt function attributes are used together.
	* gcc/doc/extend.texi: Update documentation on the critical attribute.

	gcc/testsuite/ChangeLog:

	* gcc.target/msp430/critical-interrupt.c: New test.

From-SVN: r267467

gcc/ChangeLog

+2018-12-29  Jozef Lawrynowicz  <jozef.l@mittosystems.com>
+
+	* config/msp430/msp430.c (msp430_attr): Warn when the critical and
+	interrupt function attributes are used together.
+	* gcc/doc/extend.texi: Update documentation on the critical attribute.
+
 2018-12-29  John David Anglin  <danglin@gcc.gnu.org>
 
-        * config.gcc (hppa*64*-*-linux*): Add pa/t-pa to tmake_file.  Define
-        d_target_objs.
+	* config.gcc (hppa*64*-*-linux*): Add pa/t-pa to tmake_file.  Define
+	d_target_objs.
 	(hppa*-*-openbsd*): Likewise.
 	(hppa[12]*-*-hpux10*): Likewise.
 	(hppa*64*-*-hpux11*): Likewise.

gcc/config/msp430/msp430.c

@@ -1946,6 +1946,13 @@ msp430_attr (tree * node,
 	  TREE_USED (* node) = 1;
 	  DECL_PRESERVE_P (* node) = 1;
 	}
+      if (is_critical_func (* node))
+	{
+	  warning (OPT_Wattributes,
+		   "critical attribute has no effect on interrupt functions");
+	  DECL_ATTRIBUTES (*node) = remove_attribute (ATTR_CRIT,
+						      DECL_ATTRIBUTES (* node));
+	}
     }
   else if (TREE_NAME_EQ (name, ATTR_REENT))
     {
@@ -1960,6 +1967,8 @@ msp430_attr (tree * node,
 	message = "naked functions cannot be critical";
       else if (is_reentrant_func (* node))
 	message = "reentrant functions cannot be critical";
+      else if (is_interrupt_func ( *node))
+	message = "critical attribute has no effect on interrupt functions";
     }
   else if (TREE_NAME_EQ (name, ATTR_NAKED))
     {

gcc/doc/extend.texi

@@ -4978,8 +4978,12 @@ These function attributes are supported by the MSP430 back end:
 @cindex @code{critical} function attribute, MSP430
 Critical functions disable interrupts upon entry and restore the
 previous interrupt state upon exit.  Critical functions cannot also
-have the @code{naked} or @code{reentrant} attributes.  They can have
-the @code{interrupt} attribute.
+have the @code{naked}, @code{reentrant} or @code{interrupt} attributes.
+
+The MSP430 hardware ensures that interrupts are disabled on entry to
+@code{interrupt} functions, and restores the previous interrupt state
+on exit. The @code{critical} attribute is therefore redundant on
+@code{interrupt} functions.
 
 @item interrupt
 @cindex @code{interrupt} function attribute, MSP430

gcc/testsuite/ChangeLog

+2018-12-29  Jozef Lawrynowicz  <jozef.l@mittosystems.com>
+
+	* gcc.target/msp430/critical-interrupt.c: New test.
+
 2018-12-29  Steven G. Kargl  <kargl@gcc.gnu.org>
 
 	PR fortran/88342

gcc/testsuite/gcc.target/msp430/critical-interrupt.c

+/* { dg-do compile } */
+/* { dg-final { scan-assembler-not "attributes.*critical" } } */
+
+void __attribute__((interrupt,critical))
+fn1 (void)
+{ /* { dg-warning "critical attribute has no effect on interrupt functions" } */
+}
+
+void __attribute__((critical,interrupt))
+fn2 (void)
+{ /* { dg-warning "critical attribute has no effect on interrupt functions" } */
+}