can_implement_as_sibling_call_p REG_PARM_STACK_SPACE check

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, but on
PowerPC we can tail call if the callee has less or equal
REG_PARM_STACK_SPACE than the caller, as demonstrated by the
testcase.  So we should use

  /* If reg parm stack space increases, we cannot sibcall.  */
  if (REG_PARM_STACK_SPACE (decl ? decl : fntype)
      > INCOMING_REG_PARM_STACK_SPACE (current_function_decl))

and note the change to use INCOMING_REG_PARM_STACK_SPACE.
REG_PARM_STACK_SPACE has always been wrong there for PowerPC.  See
https://gcc.gnu.org/pipermail/gcc-patches/2014-May/389867.html for why
if you're curious.  Not that it matters, because PowerPC can do
without this check entirely, relying on a stack slot test in generic
code.

a) The generic code checks that arg passing stack in the callee is not
   greater than that in the caller, and,
b) ELFv2 only allocates reg_parm_stack_space when some parameter is
   passed on the stack.
Point (b) means that zero reg_parm_stack_space implies zero stack
space, and non-zero reg_parm_stack_space implies non-zero stack
space.  So the case of 0 reg_parm_stack_space in the caller and 64 in
the callee will be caught by (a).

gcc/
	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.

gcc/testsuite/
	PR middle-end/97267
	* gcc.target/powerpc/pr97267.c: New test.

diff --git a/gcc/calls.c b/gcc/calls.c
index a8f459632f2f4f9fec667a5f697f6f825b833210..1a7632d2d4867faed8ad3e74e61deb1050bddfb6 100644 (file)
--- 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 f32b6308b5811b8ceb8f7884a78b8ca33c48ee79..b20d24bb888691030e178e59059b387d40e5a84e 100644 (file)
--- 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 8aa9516edea66a27e8b810b2fbf4964c9161a943..caa9b9d5ac1abc083d3ce2e896108edf3798c9d1 100644 (file)
--- 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/testsuite/gcc.target/powerpc/pr97267.c b/gcc/testsuite/gcc.target/powerpc/pr97267.c
new file mode 100644 (file)
index 0000000..cab4624
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr97267.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+static int __attribute__ ((__noclone__, __noinline__))
+reg_args (int j1, int j2, int j3, int j4, int j5, int j6, int j7, int j8)
+{
+  return j1 + j2 + j3 + j4 + j5 + j6 + j7 + j8;
+}
+
+int __attribute__ ((__noclone__, __noinline__))
+stack_args (int j1, int j2, int j3, int j4, int j5, int j6, int j7, int j8,
+           int j9)
+{
+  if (j9 == 0)
+    return 0;
+  return reg_args (j1, j2, j3, j4, j5, j6, j7, j8);
+}
+
+/* { dg-final { scan-assembler-not {(?n)^\s+bl\s} } } */