[PATCH 1/2] can_implement_as_sibling_call_p REG_PARM_STACK_SPACE check V2

[Alan Modra <amodra@gmail.com>]

On Sat, Oct 31, 2020 at 12:10:35AM +1030, Alan Modra wrote:
> Would it be better if I post the patches again, restructuring them as
> 1) completely no functional change just moving the existing condition
>    to the powerpc and i386 target hooks, and
> 2) twiddling the powerpc target hook?

The no function change patch.

This moves an #ifdef block of code from calls.c to
targetm.function_ok_for_sibcall.  Only two targets, x86 and rs6000,
define REG_PARM_STACK_SPACE or OUTGOING_REG_PARM_STACK_SPACE macros
that might vary depending on the called function.  Macros like
UNITS_PER_WORD don't change over a function boundary, nor does the
MIPS ABI, nor does TARGET_64BIT on PA-RISC.  Other targets are even
more trivially proven to not need the calls.c code.

Besides cleaning up a small piece of #ifdef code, the motivation for
this patch is to allow tail calls on PowerPC for functions that
require less reg_parm_stack_space than their caller.  The original
code in calls.c only permitted tail calls when exactly equal.  That
will be done in a followup patch (removing the code added to
rs6000-logue.c in this patch).

Bootstrapped and regression tested powerpc64le-linux, powerpc64-linux,
and x86_64-linux.  OK?

	PR middle-end/97267
	* calls.h (maybe_complain_about_tail_call): Declare.
	* calls.c (maybe_complain_about_tail_call): Make global.
	(can_implement_as_sibling_call_p): Delete reg_parm_stack_space
	param.  Adjust caller.  Move REG_PARM_STACK_SPACE check to..
	* config/i386/i386.c (ix86_function_ok_for_sibcall): ..here, and..
	* config/rs6000/rs6000-logue.c (rs6000_function_ok_for_sibcall): ..
	here.

diff --git a/gcc/calls.c b/gcc/calls.c
index a8f459632f2..1a7632d2d48 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -1922,7 +1922,7 @@ maybe_warn_nonstring_arg (tree fndecl, tree exp)
 /* Issue an error if CALL_EXPR was flagged as requiring
    tall-call optimization.  */
 
-static void
+void
 maybe_complain_about_tail_call (tree call_expr, const char *reason)
 {
   gcc_assert (TREE_CODE (call_expr) == CALL_EXPR);
@@ -3525,7 +3525,6 @@ static bool
 can_implement_as_sibling_call_p (tree exp,
 				 rtx structure_value_addr,
 				 tree funtype,
-				 int reg_parm_stack_space ATTRIBUTE_UNUSED,
 				 tree fndecl,
 				 int flags,
 				 tree addr,
@@ -3550,20 +3549,6 @@ can_implement_as_sibling_call_p (tree exp,
       return false;
     }
 
-#ifdef REG_PARM_STACK_SPACE
-  /* If outgoing reg parm stack space changes, we cannot do sibcall.  */
-  if (OUTGOING_REG_PARM_STACK_SPACE (funtype)
-      != OUTGOING_REG_PARM_STACK_SPACE (TREE_TYPE (current_function_decl))
-      || (reg_parm_stack_space != REG_PARM_STACK_SPACE (current_function_decl)))
-    {
-      maybe_complain_about_tail_call (exp,
-				      "inconsistent size of stack space"
-				      " allocated for arguments which are"
-				      " passed in registers");
-      return false;
-    }
-#endif
-
   /* Check whether the target is able to optimize the call
      into a sibcall.  */
   if (!targetm.function_ok_for_sibcall (fndecl, exp))
@@ -4088,7 +4073,6 @@ expand_call (tree exp, rtx target, int ignore)
     try_tail_call = can_implement_as_sibling_call_p (exp,
 						     structure_value_addr,
 						     funtype,
-						     reg_parm_stack_space,
 						     fndecl,
 						     flags, addr, args_size);
 
diff --git a/gcc/calls.h b/gcc/calls.h
index f32b6308b58..b20d24bb888 100644
--- a/gcc/calls.h
+++ b/gcc/calls.h
@@ -133,6 +133,7 @@ extern bool reference_callee_copied (CUMULATIVE_ARGS *,
 extern void maybe_warn_alloc_args_overflow (tree, tree, tree[2], int[2]);
 extern tree get_attr_nonstring_decl (tree, tree * = NULL);
 extern bool maybe_warn_nonstring_arg (tree, tree);
+extern void maybe_complain_about_tail_call (tree, const char *);
 enum size_range_flags
   {
    /* Set to consider zero a valid range.  */
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 502d24057b5..809c145b638 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -939,6 +939,19 @@ ix86_function_ok_for_sibcall (tree decl, tree exp)
       decl_or_type = type;
     }
 
+  /* If outgoing reg parm stack space changes, we cannot do sibcall.  */
+  if ((OUTGOING_REG_PARM_STACK_SPACE (type)
+       != OUTGOING_REG_PARM_STACK_SPACE (TREE_TYPE (current_function_decl)))
+      || (REG_PARM_STACK_SPACE (decl_or_type)
+	  != REG_PARM_STACK_SPACE (current_function_decl)))
+    {
+      maybe_complain_about_tail_call (exp,
+				      "inconsistent size of stack space"
+				      " allocated for arguments which are"
+				      " passed in registers");
+      return false;
+    }
+
   /* Check that the return value locations are the same.  Like
      if we are returning floats on the 80387 register stack, we cannot
      make a sibcall from a function that doesn't return a float to a
diff --git a/gcc/config/rs6000/rs6000-logue.c b/gcc/config/rs6000/rs6000-logue.c
index d90cd5736e1..61eb7ce7ade 100644
--- a/gcc/config/rs6000/rs6000-logue.c
+++ b/gcc/config/rs6000/rs6000-logue.c
@@ -30,6 +30,7 @@
 #include "df.h"
 #include "tm_p.h"
 #include "ira.h"
+#include "calls.h"
 #include "print-tree.h"
 #include "varasm.h"
 #include "explow.h"
@@ -1133,6 +1134,19 @@ rs6000_function_ok_for_sibcall (tree decl, tree exp)
   else
     fntype = TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (exp)));
 
+  /* If outgoing reg parm stack space changes, we cannot do sibcall.  */
+  if ((OUTGOING_REG_PARM_STACK_SPACE (fntype)
+       != OUTGOING_REG_PARM_STACK_SPACE (TREE_TYPE (current_function_decl)))
+      || (REG_PARM_STACK_SPACE (decl ? decl : fntype)
+	  != REG_PARM_STACK_SPACE (current_function_decl)))
+    {
+      maybe_complain_about_tail_call (exp,
+				      "inconsistent size of stack space"
+				      " allocated for arguments which are"
+				      " passed in registers");
+      return false;
+    }
+
   /* We can't do it if the called function has more vector parameters
      than the current function; there's nowhere to put the VRsave code.  */
   if (TARGET_ALTIVEC_ABI

-- 
Alan Modra
Australia Development Lab, IBM