[gomp4] Fix an ICE involving OpenACC routines inside broken fortran functions.

[Cesar Philippidis <cesar@codesourcery.com>]

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I encountered an ICE when the fortran FE tries to parse an OpenACC
routine directive when the containing function has a syntax error. E.g.

  integer function f1

is missing an argument list, so the fortran FE will not create a
function symbol for f1. Consequently, the OpenACC routine parser cannot
register the routine directive with any function, so it hit a
gcc_unreachable.

This patch replaces that gcc_unreachable with a match_error. While the
syntax of the routine directive may be correct, it is still an error to
have a dangling acc routine directive not associated with a function.

I've applied this patch to gomp-4_0-branch.

Cesar

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2017-04-27  Cesar Philippidis  <cesar@codesourcery.com>

	gcc/fortran/
	* openmp.c (gfc_match_oacc_routine): Don't match OpenACC routines
	when the current function failed to parse due to a syntax error.

	gcc/testsuite/
	* gfortran.dg/goacc/routine-10.f90: New test.


diff --git a/gcc/fortran/openmp.c b/gcc/fortran/openmp.c
index 0aecda4..72c6669 100644
--- a/gcc/fortran/openmp.c
+++ b/gcc/fortran/openmp.c
@@ -2576,7 +2576,9 @@ gfc_match_oacc_routine (void)
 	goto cleanup;
     }
   else
-    gcc_unreachable ();
+    /* Something has gone wrong.  Perhaps there was a syntax error
+       in the program-stmt.  */
+    goto cleanup;
 
   if (n)
     n->clauses = c;
diff --git a/gcc/testsuite/gfortran.dg/goacc/routine-10.f90 b/gcc/testsuite/gfortran.dg/goacc/routine-10.f90
new file mode 100644
index 0000000..4d8b5ba
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/goacc/routine-10.f90
@@ -0,0 +1,8 @@
+! Ensure that GFortran doesn't ICE with incomplete function
+! definitions.
+
+! { dg-do compile }
+
+integer function f1 ! { dg-error "Expected formal argument list in function definition" }
+  !$acc routine ! { dg-error "Unclassifiable OpenACC directive" }
+end function f1 ! { dg-error "Expecting END PROGRAM statement" }