Patchwork [RS6000] out-of-line save/restore conditions

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Submitter Alan Modra
Date May 21, 2012, 5:14 a.m.
Message ID <20120521051402.GE3285@bubble.grove.modra.org>
Download mbox | patch
Permalink /patch/160313/
State New
Headers show

Comments

Alan Modra - May 21, 2012, 5:14 a.m.
Currently, powerpc-linux gcc -Os -mno-multiple uses out-of-linux gpr
save and restore functions when saving/restoring just one gpr.  That's
quite silly since the function call requires more instructions and is
slower than an inline save/restore.  The only case where it might win
is when no fprs are restored and the restore function can tear down
the frame and exit (also loading up lr on ppc64).  I guess that's how
GP_SAVE_INLINE came to be like it is, ie. it's optimised for the
common case using ldm in the prologue and no fprs.  Still, it isn't
difficult to choose the best combination in all cases, but it does
mean different logic is needed for restores.  I could have implemented
GP_RESTORE_INLINE and FP_RESORE_INLINE macros but it seemed simpler to
just move everything into the one place the macros are invoked.  AIX
and Darwin register cutoff doesn't change with this patch.

This patch also enables out-of-line restores in cases that were
previously disabled due to using inline saves.

Bootstrapped and regression tested powerpc-linux.  OK to apply?

	* aix.h (FP_SAVE_INLINE, GP_SAVE_INLINE): Delete.
	* darwin.h (FP_SAVE_INLINE, GP_SAVE_INLINE): Delete.
	* sysv4.h (FP_SAVE_INLINE, GP_SAVE_INLINE, V_SAVE_INLINE): Delete.
	* config/rs6000/rs6000.c (V_SAVE_INLINE): Delete.
	(rs6000_savres_strategy): Reimplement GP/FP/V_SAVE_INLINE logic.
	For ELF targets, use out-of-line restores for -Os and any number
	of regs if the restore exits, and out-of-line gp save for two or
	more regs.  Use save_reg_p to test for holes in reg restore set.
	Replace "#if" with "if".
David Edelsohn - May 21, 2012, 3:36 p.m.
On Mon, May 21, 2012 at 1:14 AM, Alan Modra <amodra@gmail.com> wrote:
> Currently, powerpc-linux gcc -Os -mno-multiple uses out-of-line gpr
> save and restore functions when saving/restoring just one gpr.  That's
> quite silly since the function call requires more instructions and is
> slower than an inline save/restore.  The only case where it might win
> is when no fprs are restored and the restore function can tear down
> the frame and exit (also loading up lr on ppc64).  I guess that's how
> GP_SAVE_INLINE came to be like it is, ie. it's optimised for the
> common case using ldm in the prologue and no fprs.  Still, it isn't
> difficult to choose the best combination in all cases, but it does
> mean different logic is needed for restores.  I could have implemented
> GP_RESTORE_INLINE and FP_RESORE_INLINE macros but it seemed simpler to
> just move everything into the one place the macros are invoked.  AIX
> and Darwin register cutoff doesn't change with this patch.
>
> This patch also enables out-of-line restores in cases that were
> previously disabled due to using inline saves.
>
> Bootstrapped and regression tested powerpc-linux.  OK to apply?
>
>        * aix.h (FP_SAVE_INLINE, GP_SAVE_INLINE): Delete.
>        * darwin.h (FP_SAVE_INLINE, GP_SAVE_INLINE): Delete.
>        * sysv4.h (FP_SAVE_INLINE, GP_SAVE_INLINE, V_SAVE_INLINE): Delete.
>        * config/rs6000/rs6000.c (V_SAVE_INLINE): Delete.
>        (rs6000_savres_strategy): Reimplement GP/FP/V_SAVE_INLINE logic.
>        For ELF targets, use out-of-line restores for -Os and any number
>        of regs if the restore exits, and out-of-line gp save for two or
>        more regs.  Use save_reg_p to test for holes in reg restore set.
>        Replace "#if" with "if".

Okay.

Thanks, David

Patch

Index: gcc/config/rs6000/aix.h
===================================================================
--- gcc/config/rs6000/aix.h	(revision 187699)
+++ gcc/config/rs6000/aix.h	(working copy)
@@ -207,11 +207,6 @@ 
   { "link_syscalls",            LINK_SYSCALLS_SPEC },			\
   { "link_libg",                LINK_LIBG_SPEC }
 
-/* Define cutoff for using external functions to save floating point.  */
-#define FP_SAVE_INLINE(FIRST_REG) ((FIRST_REG) == 62 || (FIRST_REG) == 63)
-/* And similarly for general purpose registers.  */
-#define GP_SAVE_INLINE(FIRST_REG) ((FIRST_REG) < 32)
-
 #define PROFILE_HOOK(LABEL)   output_profile_hook (LABEL)
 
 /* No version of AIX fully supports AltiVec or 64-bit instructions in
Index: gcc/config/rs6000/darwin.h
===================================================================
--- gcc/config/rs6000/darwin.h	(revision 187699)
+++ gcc/config/rs6000/darwin.h	(working copy)
@@ -173,16 +173,6 @@ 
   (RS6000_ALIGN (crtl->outgoing_args_size, 16)		\
    + (STACK_POINTER_OFFSET))
 
-/* Define cutoff for using out-of-line functions to save registers.
-   Currently on Darwin, we implement FP and GPR out-of-line-saves plus the
-   special routine for 'save everything'.  */
-
-#undef FP_SAVE_INLINE
-#define FP_SAVE_INLINE(FIRST_REG) ((FIRST_REG) > 60 && (FIRST_REG) < 64)
-
-#undef GP_SAVE_INLINE
-#define GP_SAVE_INLINE(FIRST_REG) ((FIRST_REG) > 29 && (FIRST_REG) < 32)
-
 /* Darwin uses a function call if everything needs to be saved/restored.  */
 
 #undef WORLD_SAVE_P
Index: gcc/config/rs6000/sysv4.h
===================================================================
--- gcc/config/rs6000/sysv4.h	(revision 187699)
+++ gcc/config/rs6000/sysv4.h	(working copy)
@@ -243,19 +243,6 @@ 
 #define	BYTES_BIG_ENDIAN (TARGET_BIG_ENDIAN)
 #define	WORDS_BIG_ENDIAN (TARGET_BIG_ENDIAN)
 
-/* Define cutoff for using external functions to save floating point.
-   When optimizing for size, use external functions when profitable.  */
-#define FP_SAVE_INLINE(FIRST_REG) ((FIRST_REG) == 62			\
-				   || (FIRST_REG) == 63			\
-				   || !optimize_size)
-
-/* And similarly for general purpose registers.  */
-#define GP_SAVE_INLINE(FIRST_REG) (!optimize_size)
-
-/* And vector registers.  */
-#define V_SAVE_INLINE(FIRST_REG) ((FIRST_REG) == LAST_ALTIVEC_REGNO	\
-				  || !optimize_size)
-
 /* Put jump tables in read-only memory, rather than in .text.  */
 #define JUMP_TABLES_IN_TEXT_SECTION 0
 
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c	(revision 187699)
+++ gcc/config/rs6000/rs6000.c	(working copy)
@@ -17443,10 +17294,6 @@ 
   REST_INLINE_VRS = 0x200
 };
 
-#ifndef V_SAVE_INLINE
-#define V_SAVE_INLINE(FIRST_REG) 1
-#endif
-
 static int
 rs6000_savres_strategy (rs6000_stack_t *info,
 			bool using_static_chain_p)
@@ -17468,7 +17315,6 @@ 
 		 | SAVE_INLINE_VRS | REST_INLINE_VRS);
 
   if (info->first_fp_reg_save == 64
-      || FP_SAVE_INLINE (info->first_fp_reg_save)
       /* The out-of-line FP routines use double-precision stores;
 	 we can't use those routines if we don't have such stores.  */
       || (TARGET_HARD_FLOAT && !TARGET_DOUBLE_FLOAT)
@@ -17476,26 +17322,80 @@ 
     strategy |= SAVE_INLINE_FPRS | REST_INLINE_FPRS;
 
   if (info->first_gp_reg_save == 32
-      || GP_SAVE_INLINE (info->first_gp_reg_save)
       || (!(strategy & SAVRES_MULTIPLE)
 	  && global_regs_p (info->first_gp_reg_save, 32)))
     strategy |= SAVE_INLINE_GPRS | REST_INLINE_GPRS;
 
   if (info->first_altivec_reg_save == LAST_ALTIVEC_REGNO + 1
-      || V_SAVE_INLINE (info->first_altivec_reg_save)
       || global_regs_p (info->first_altivec_reg_save, LAST_ALTIVEC_REGNO + 1))
     strategy |= SAVE_INLINE_VRS | REST_INLINE_VRS;
 
+  /* Define cutoff for using out-of-line functions to save registers.  */
+  if (DEFAULT_ABI == ABI_V4 || TARGET_ELF)
+    {
+      if (!optimize_size)
+	{
+	  strategy |= SAVE_INLINE_FPRS | REST_INLINE_FPRS;
+	  strategy |= SAVE_INLINE_GPRS | REST_INLINE_GPRS;
+	  strategy |= SAVE_INLINE_VRS | REST_INLINE_VRS;
+	}
+      else
+	{
+	  /* Prefer out-of-line restore if it will exit.  */
+	  if (info->first_fp_reg_save > 61)
+	    strategy |= SAVE_INLINE_FPRS;
+	  if (info->first_gp_reg_save > 29)
+	    {
+	      if (info->first_fp_reg_save == 64)
+		strategy |= SAVE_INLINE_GPRS;
+	      else
+		strategy |= SAVE_INLINE_GPRS | REST_INLINE_GPRS;
+	    }
+	  if (info->first_altivec_reg_save == LAST_ALTIVEC_REGNO)
+	    strategy |= SAVE_INLINE_VRS | REST_INLINE_VRS;
+	}
+    }
+  else if (DEFAULT_ABI == ABI_DARWIN)
+    {
+      if (info->first_fp_reg_save > 60)
+	strategy |= SAVE_INLINE_FPRS | REST_INLINE_FPRS;
+      if (info->first_gp_reg_save > 29)
+	strategy |= SAVE_INLINE_GPRS | REST_INLINE_GPRS;
+      strategy |= SAVE_INLINE_VRS | REST_INLINE_VRS;
+    }
+  else
+    {
+      gcc_checking_assert (DEFAULT_ABI == ABI_AIX);
+      if (info->first_fp_reg_save > 61)
+	strategy |= SAVE_INLINE_FPRS | REST_INLINE_FPRS;
+      strategy |= SAVE_INLINE_GPRS | REST_INLINE_GPRS;
+      strategy |= SAVE_INLINE_VRS | REST_INLINE_VRS;
+    }
+
   /* Don't bother to try to save things out-of-line if r11 is occupied
      by the static chain.  It would require too much fiddling and the
      static chain is rarely used anyway.  FPRs are saved w.r.t the stack
      pointer on Darwin, and AIX uses r1 or r12.  */
   if (using_static_chain_p && DEFAULT_ABI != ABI_AIX)
-    strategy |= ((DEFAULT_ABI == ABI_DARWIN
-		  ? 0 : SAVE_INLINE_FPRS | REST_INLINE_FPRS)
+    strategy |= ((DEFAULT_ABI == ABI_DARWIN ? 0 : SAVE_INLINE_FPRS)
 		 | SAVE_INLINE_GPRS
 		 | SAVE_INLINE_VRS | REST_INLINE_VRS);
 
+  /* We can only use the out-of-line routines to restore if we've
+     saved all the registers from first_fp_reg_save in the prologue.
+     Otherwise, we risk loading garbage.  */
+  if ((strategy & (SAVE_INLINE_FPRS | REST_INLINE_FPRS)) == SAVE_INLINE_FPRS)
+    {
+      int i;
+
+      for (i = info->first_fp_reg_save; i < 64; i++)
+	if (!save_reg_p (i))
+	  {
+	    strategy |= REST_INLINE_FPRS;
+	    break;
+	  }
+    }
+
   /* If we are going to use store multiple, then don't even bother
      with the out-of-line routines, since the store-multiple
      instruction will always be smaller.  */
@@ -17525,13 +17426,6 @@ 
 	  || info->first_fp_reg_save != 64))
     strategy |= REST_INLINE_GPRS;
 
-  /* We can only use load multiple or the out-of-line routines to
-     restore if we've used store multiple or out-of-line routines
-     in the prologue, i.e. if we've saved all the registers from
-     first_gp_reg_save.  Otherwise, we risk loading garbage.  */
-  if ((strategy & (SAVE_INLINE_GPRS | SAVRES_MULTIPLE)) == SAVE_INLINE_GPRS)
-    strategy |= REST_INLINE_GPRS;
-
   /* Saving CR interferes with the exit routines used on the SPE, so
      just punt here.  */
   if (TARGET_SPE_ABI
@@ -17539,19 +17433,34 @@ 
       && info->cr_save_p)
     strategy |= REST_INLINE_GPRS;
 
-#if defined (POWERPC_LINUX) || defined (POWERPC_FREEBSD)
-  if (TARGET_64BIT)
+  /* We can only use load multiple or the out-of-line routines to
+     restore if we've used store multiple or out-of-line routines
+     in the prologue, i.e. if we've saved all the registers from
+     first_gp_reg_save.  Otherwise, we risk loading garbage.  */
+  if ((strategy & (SAVE_INLINE_GPRS | REST_INLINE_GPRS | SAVRES_MULTIPLE))
+      == SAVE_INLINE_GPRS)
     {
+      int i;
+
+      for (i = info->first_gp_reg_save; i < 32; i++)
+	if (!save_reg_p (i))
+	  {
+	    strategy |= REST_INLINE_GPRS;
+	    break;
+	  }
+    }
+
+  if (TARGET_ELF && TARGET_64BIT)
+    {
       if (!(strategy & SAVE_INLINE_FPRS))
 	strategy |= SAVE_NOINLINE_FPRS_SAVES_LR;
       else if (!(strategy & SAVE_INLINE_GPRS)
 	       && info->first_fp_reg_save == 64)
 	strategy |= SAVE_NOINLINE_GPRS_SAVES_LR;
     }
-#else
-  if (TARGET_AIX && !(strategy & REST_INLINE_FPRS))
+  else if (TARGET_AIX && !(strategy & REST_INLINE_FPRS))
     strategy |= REST_NOINLINE_FPRS_DOESNT_RESTORE_LR;
-#endif
+
   if (TARGET_MACHO && !(strategy & SAVE_INLINE_FPRS))
     strategy |= SAVE_NOINLINE_FPRS_SAVES_LR;