[ARM HARD VFP] Tidy up libcall detection for using Base AAPCS

[Richard Earnshaw <rearnsha at arm dot com>]

In the hard-fp variant of the AAPCS certain libcalls must continue to be
called using the base standard; we need to detect these individually and
do the right thing (most of them will never in practice be called, but a
few can).  We currently do this by explicitly testing the libcall
argument against each possible candidate, but that's quite expensive and
has to be done in two places.

I've reworked this bit of code to use a small hash table which is
initialized once with all the functions that require this treatment.
This means we can check the libcalls in constant time and also provides
a single place that knows about this rule.

tested on arm-eabi (hard-vfp) and applied to the arm hard-vfp branch.

R.

2009-08-04  Richard Earnshaw  <rearnsha@arm.com>

	* arm.c (libcall_eq): New function.
	(libcall_hash): New function.
	(add_libcall): New function.
	(arm_libcall_uses_aapcs_base): New function.
	(arm_libcall_value): Use arm_libcall_uses_aapcs_base to check for
	libcalls using the base PCS.
	(arm_init_cumulative_args): Likewise.

Index: arm.c
===================================================================
--- arm.c	(revision 150401)
+++ arm.c	(working copy)
@@ -3141,6 +3141,71 @@
   return LIBCALL_VALUE (mode);
 }
 
+static int
+libcall_eq (const void *p1, const void *p2)
+{
+  return rtx_equal_p ((const_rtx) p1, (const_rtx) p2);
+}
+
+static hashval_t
+libcall_hash (const void *p1)
+{
+  return hash_rtx ((const_rtx) p1, VOIDmode, NULL, NULL, FALSE);
+}
+
+static void
+add_libcall (htab_t htab, rtx libcall)
+{
+  *htab_find_slot (htab, libcall, INSERT) = libcall;
+}
+
+static bool
+arm_libcall_uses_aapcs_base (rtx libcall)
+{
+  static bool init_done = false;
+  static htab_t libcall_htab;
+
+  if (!init_done)
+    {
+      init_done = true;
+
+      libcall_htab = htab_create (31, libcall_hash, libcall_eq,
+				  NULL);
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (sfloat_optab, SFmode, SImode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (sfloat_optab, DFmode, SImode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (sfloat_optab, SFmode, DImode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (sfloat_optab, DFmode, DImode));
+      
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (ufloat_optab, SFmode, SImode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (ufloat_optab, DFmode, SImode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (ufloat_optab, SFmode, DImode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (ufloat_optab, DFmode, DImode));
+
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (sext_optab, SFmode, HFmode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (trunc_optab, HFmode, SFmode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (sfix_optab, DImode, DFmode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (ufix_optab, DImode, DFmode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (sfix_optab, DImode, SFmode));
+      add_libcall (libcall_htab,
+		   convert_optab_libfunc (ufix_optab, DImode, SFmode));
+    }
+
+  return libcall && htab_find (libcall_htab, libcall) != NULL;
+}
+
 rtx
 arm_libcall_value (enum machine_mode mode, rtx libcall)
 {
@@ -3149,22 +3214,9 @@
     {
       /* The following libcalls return their result in integer registers,
 	 even though they return a floating point value.  */
-      if (rtx_equal_p (libcall,
-		       convert_optab_libfunc (sfloat_optab, mode, SImode))
-	  || rtx_equal_p (libcall,
-			  convert_optab_libfunc (ufloat_optab, mode, SImode))
-	  || rtx_equal_p (libcall,
-			  convert_optab_libfunc (sfloat_optab, mode, DImode))
-	  || rtx_equal_p (libcall,
-			  convert_optab_libfunc (ufloat_optab, mode, DImode))
-	  || rtx_equal_p (libcall,
-			  convert_optab_libfunc (trunc_optab, HFmode, SFmode))
-	  || rtx_equal_p (libcall,
-			  convert_optab_libfunc (sext_optab, SFmode, HFmode)))
+      if (arm_libcall_uses_aapcs_base (libcall))
 	return gen_rtx_REG (mode, ARG_REGISTER(1));
 
-      /* XXX There are other libcalls that return in integer registers,
-	 but I think they are all handled by hard insns.  */
     }
 
   return LIBCALL_VALUE (mode);
@@ -4077,22 +4129,7 @@
 
   if (pcum->pcs_variant <= ARM_PCS_AAPCS_LOCAL)
     {
-      /* XXX We should also detect some library calls here and handle
-	 them using the base rules too; for example the floating point
-	 support functions always work this way.  */
-
-       if (rtx_equal_p (libname,
-		       convert_optab_libfunc (sfix_optab, DImode, DFmode))
-	  || rtx_equal_p (libname,
-			  convert_optab_libfunc (ufix_optab, DImode, DFmode))
-	  || rtx_equal_p (libname,
-			  convert_optab_libfunc (sfix_optab, DImode, SFmode))
-	  || rtx_equal_p (libname,
-			  convert_optab_libfunc (ufix_optab, DImode, SFmode))
-	  || rtx_equal_p (libname,
-			  convert_optab_libfunc (trunc_optab, HFmode, SFmode))
-	  || rtx_equal_p (libname,
-			  convert_optab_libfunc (sext_optab, SFmode, HFmode)))
+      if (arm_libcall_uses_aapcs_base (libname))
 	pcum->pcs_variant = ARM_PCS_AAPCS;
  
       pcum->aapcs_ncrn = pcum->aapcs_next_ncrn = 0;