re PR fortran/90329 (Incompatibility between gfortran and C lapack calls)

	PR fortran/90329
	* lang.opt (fbroken-callers): Remove.
	(ftail-call-workaround, ftail-call-workaround=): New options.
	* gfortran.h (struct gfc_namespace): Add implicit_interface_calls.
	* interface.c (gfc_procedure_use): Set implicit_interface_calls
	for calls to implicit interface procedures.
	* trans-decl.c (create_function_arglist): Use flag_tail_call_workaround
	instead of flag_broken_callers.  If it is not 2, also require
	sym->ns->implicit_interface_calls.
	* invoke.texi (fbroken-callers): Remove documentation.
	(ftail-call-workaround, ftail-call-workaround=): Document.

From-SVN: r271738

gcc/fortran/ChangeLog

+2019-05-29  Jakub Jelinek  <jakub@redhat.com>
+
+	PR fortran/90329
+	* lang.opt (fbroken-callers): Remove.
+	(ftail-call-workaround, ftail-call-workaround=): New options.
+	* gfortran.h (struct gfc_namespace): Add implicit_interface_calls.
+	* interface.c (gfc_procedure_use): Set implicit_interface_calls
+	for calls to implicit interface procedures.
+	* trans-decl.c (create_function_arglist): Use flag_tail_call_workaround
+	instead of flag_broken_callers.  If it is not 2, also require
+	sym->ns->implicit_interface_calls.
+	* invoke.texi (fbroken-callers): Remove documentation.
+	(ftail-call-workaround, ftail-call-workaround=): Document.
+
 2019-05-26  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/90539

gcc/fortran/gfortran.h

@@ -1866,6 +1866,9 @@ typedef struct gfc_namespace
 
   /* Set to 1 for !$ACC ROUTINE namespaces.  */
   unsigned oacc_routine:1;
+
+  /* Set to 1 if there are any calls to procedures with implicit interface.  */
+  unsigned implicit_interface_calls:1;
 }
 gfc_namespace;
 

gcc/fortran/interface.c

@@ -3686,6 +3686,7 @@ gfc_procedure_use (gfc_symbol *sym, gfc_actual_arglist **ap, locus *where)
 	gfc_warning (OPT_Wimplicit_procedure,
 		     "Procedure %qs called at %L is not explicitly declared",
 		     sym->name, where);
+      gfc_find_proc_namespace (sym->ns)->implicit_interface_calls = 1;
     }
 
   if (sym->attr.if_source == IFSRC_UNKNOWN)

gcc/fortran/invoke.texi

@@ -181,7 +181,8 @@ and warnings}.
 @item Code Generation Options
 @xref{Code Gen Options,,Options for code generation conventions}.
 @gccoptlist{-faggressive-function-elimination -fblas-matmul-limit=@var{n} @gol
--fbounds-check -fbroken-callers -fcheck-array-temporaries @gol
+-fbounds-check -ftail-call-workaround -ftail-call-workaround=@var{n} @gol
+-fcheck-array-temporaries @gol
 -fcheck=@var{<all|array-temps|bounds|do|mem|pointer|recursion>} @gol
 -fcoarray=@var{<none|single|lib>} -fexternal-blas -ff2c
 -ffrontend-loop-interchange @gol
@@ -1622,8 +1623,9 @@ warnings for generated array temporaries.
 @c Note: This option is also referred in gcc's manpage
 Deprecated alias for @option{-fcheck=bounds}.
 
-@item -fbroken-callers
-@opindex @code{broken-callers}
+@item -ftail-call-workaround
+@itemx -ftail-call-workaround=@var{n}
+@opindex @code{tail-call-workaround}
 Some C interfaces to Fortran codes violate the gfortran ABI by
 omitting the hidden character length arguments as described in
 @xref{Argument passing conventions}.  This can lead to crashes
@@ -1631,7 +1633,11 @@ because pushing arguments for tail calls can overflow the stack.
 
 To provide a workaround for existing binary packages, this option
 disables tail call optimization for gfortran procedures with character
-arguments.
+arguments.  With @option{-ftail-call-workaround=2} tail call optimization
+is disabled in all gfortran procedures with character arguments,
+with @option{-ftail-call-workaround=1} or equivalent
+@option{-ftail-call-workaround} only in gfortran procedures with character
+arguments that call implicitly prototyped procedures.
 
 Using this option can lead to problems including crashes due to
 insufficient stack space.
@@ -1644,10 +1650,10 @@ source code.
 Support for this option will likely be withdrawn in a future release
 of gfortran.
 
-The negative form, @option{-fno-broken-callers}, can be used to
-disable this option.
+The negative form, @option{-fno-tail-call-workaround} or equivalent
+@option{-ftail-call-workaround=0}, can be used to disable this option.
 
-Default is currently @option{-fbroken-callers}, this will change
+Default is currently @option{-ftail-call-workaround}, this will change
 in future releases.
 
 @item -fcheck-array-temporaries

gcc/fortran/lang.opt

@@ -397,10 +397,6 @@ fblas-matmul-limit=
 Fortran RejectNegative Joined UInteger Var(flag_blas_matmul_limit) Init(30)
 -fblas-matmul-limit=<n>	Size of the smallest matrix for which matmul will use BLAS.
 
-fbroken-callers
-Fortran Var(flag_broken_callers) Init(1)
-Disallow tail call optimization when a calling routine may have omitted character lenghts.
-
 fcheck-array-temporaries
 Fortran
 Produce a warning at runtime if a array temporary has been created for a procedure argument.
@@ -766,6 +762,13 @@ fsign-zero
 Fortran Var(flag_sign_zero) Init(1)
 Apply negative sign to zero values.
 
+ftail-call-workaround
+Frotran Alias(ftail-call-workaround=,1,0)
+
+ftail-call-workaround=
+Fortran RejectNegative Joined UInteger IntegerRange(0, 2) Var(flag_tail_call_workaround) Init(1)
+Disallow tail call optimization when a calling routine may have omitted character lenghts.
+
 funderscoring
 Fortran Var(flag_underscoring) Init(1)
 Append underscores to externally visible names.

gcc/fortran/trans-decl.c

@@ -2520,9 +2520,12 @@ create_function_arglist (gfc_symbol * sym)
 	  /* Marking the length DECL_HIDDEN_STRING_LENGTH will lead
 	     to tail calls being disabled.  Only do that if we
 	     potentially have broken callers.  */
-	  if (flag_broken_callers && f->sym->ts.u.cl
+	  if (flag_tail_call_workaround
+	      && f->sym->ts.u.cl
 	      && f->sym->ts.u.cl->length
-	      && f->sym->ts.u.cl->length->expr_type == EXPR_CONSTANT)
+	      && f->sym->ts.u.cl->length->expr_type == EXPR_CONSTANT
+	      && (flag_tail_call_workaround == 2
+		  || f->sym->ns->implicit_interface_calls))
 	    DECL_HIDDEN_STRING_LENGTH (length) = 1;
 
 	  /* Remember the passed value.  */