Re: [PATCH] -fpic problems on PPC, a different approach

[Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>]

Am Tue, 08 Jun 1999 schrieb Richard Henderson:
>On Mon, Jun 07, 1999 at 07:26:50PM -0600, Jeffrey A Law wrote:
>> Keep track of whether or not you ever reference the pic register.  If you
>> do, then you'll need to load it up at appropriate times.  Else you ignore
>> it completely.
>
>You don't actually have to explicitly track this.  Since there
>are no hidden uses of the pic register in the ppc port, you can
>simply check regs_ever_live[PIC_OFFSET_TABLE_REGNUM] when you
>generate the function's prologue.
>
>Ignore FINALIZE_PIC -- it is a red herring.
>
>Remove all references to GOT_TOC_REGNUM.  Don't ever write to
>pic_offset_table_rtx; don't save and restore it in
>rs6000_save_machine_status.
>
>The movsi_got patterns can be streamlined; movsi_got_internal_mem
>can go away entirely.

Ok, here's my first try. Basically it should be OK, it at least compiles all
the troublesome -fpic testcases correctly. It turned out that simply checking
regs_ever_live[PIC_OFFSET_TABLE_REGNUM] is not enough, as this information
may no longer be correct after reload, if reload was the first instance to
produce pic_offset_table_rtx references. I've also marked some explicit uses of
r2, the old GOT_TOC_REGNUM, they might need some extra treatment now.

Is it possible to use something like "frame_pointer_needed ? 30 : 31" for
PIC_OFFSET_TABLE_REGNUM? This would make the unnecessary saving of r31 go away.

Franz.


Index: rs6000.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/config/rs6000/rs6000.c,v
retrieving revision 1.70.4.1
diff -u -p -r1.70.4.1 rs6000.c
--- rs6000.c	1999/05/28 02:41:43	1.70.4.1
+++ rs6000.c	1999/06/09 00:04:43
@@ -2397,142 +2411,15 @@ struct rtx_def *
 rs6000_got_register (value)
      rtx value;
 {
-  if (! current_function_uses_pic_offset_table || ! pic_offset_table_rtx)
-    {
-      if (no_new_pseudos)
-	fatal_insn ("internal error -- needed new GOT register during reload phase to load:",
-		    value);
-
-      current_function_uses_pic_offset_table = 1;
-      pic_offset_table_rtx = gen_rtx_REG (Pmode, GOT_TOC_REGNUM);
-    }
+  if (no_new_pseudos && !regs_ever_live[PIC_OFFSET_TABLE_REGNUM])
+    regs_ever_live[PIC_OFFSET_TABLE_REGNUM] = 1;
 
+  current_function_uses_pic_offset_table = 1;
   return pic_offset_table_rtx;
 }
 
-
-/* Replace all occurrences of register FROM with an new pseudo register in an insn X.
-   Store the pseudo register used in REG.
-   This is only safe during FINALIZE_PIC, since the registers haven't been setup
-   yet.  */
-
-static rtx
-rs6000_replace_regno (x, from, reg)
-     rtx x;
-     int from;
-     rtx *reg;
-{
-  register int i, j;
-  register const char *fmt;
-
-  /* Allow this function to make replacements in EXPR_LISTs.  */
-  if (!x)
-    return x;
-
-  switch (GET_CODE (x))
-    {
-    case SCRATCH:
-    case PC:
-    case CC0:
-    case CONST_INT:
-    case CONST_DOUBLE:
-    case CONST:
-    case SYMBOL_REF:
-    case LABEL_REF:
-      return x;
-
-    case REG:
-      if (REGNO (x) == from)
-	{
-	  if (! *reg)
-	    *reg = pic_offset_table_rtx = gen_reg_rtx (Pmode);
-
-	  return *reg;
-	}
-
-      return x;
-
-    default:
-      break;
-    }
-
-  fmt = GET_RTX_FORMAT (GET_CODE (x));
-  for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--)
-    {
-      if (fmt[i] == 'e')
-	XEXP (x, i) = rs6000_replace_regno (XEXP (x, i), from, reg);
-      else if (fmt[i] == 'E')
-	for (j = XVECLEN (x, i) - 1; j >= 0; j--)
-	  XVECEXP (x, i, j) = rs6000_replace_regno (XVECEXP (x, i, j), from, reg);
-    }
-
-  return x;
-}  
-
-
-/* By generating position-independent code, when two different
-   programs (A and B) share a common library (libC.a), the text of
-   the library can be shared whether or not the library is linked at
-   the same address for both programs.  In some of these
-   environments, position-independent code requires not only the use
-   of different addressing modes, but also special code to enable the
-   use of these addressing modes.
-
-   The `FINALIZE_PIC' macro serves as a hook to emit these special
-   codes once the function is being compiled into assembly code, but
-   not before.  (It is not done before, because in the case of
-   compiling an inline function, it would lead to multiple PIC
-   prologues being included in functions which used inline functions
-   and were compiled to assembly language.)  */
-
-void
-rs6000_finalize_pic ()
-{
-  /* Loop through all of the insns, replacing the special GOT_TOC_REGNUM
-     with an appropriate pseudo register.  If we find we need GOT/TOC,
-     add the appropriate init code.  */
-  if (flag_pic && (DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_SOLARIS))
-    {
-      rtx insn = get_insns ();
-      rtx reg = NULL_RTX;
-      rtx first_insn;
-      rtx last_insn = NULL_RTX;
-
-      if (GET_CODE (insn) == NOTE)
-	insn = next_nonnote_insn (insn);
-
-      first_insn = insn;
-      for ( ; insn != NULL_RTX; insn = NEXT_INSN (insn))
-	{
-	  if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
-	    {
-	      PATTERN (insn) = rs6000_replace_regno (PATTERN (insn),
-						     GOT_TOC_REGNUM,
-						     &reg);
-
-	      if (REG_NOTES (insn))
-		REG_NOTES (insn) = rs6000_replace_regno (REG_NOTES (insn),
-							 GOT_TOC_REGNUM,
-							 &reg);
-	    }
-
-	  if (GET_CODE (insn) != NOTE)
-	    last_insn = insn;
-	}
-
-      if (reg)
-	{
-	  rtx init = gen_init_v4_pic (reg);
-	  emit_insn_before (init, first_insn);
-	  if (!optimize && last_insn)
-	    emit_insn_after (gen_rtx_USE (VOIDmode, reg), last_insn);
-	}
-    }
-}
-
-
 /* Search for any occurrence of the GOT_TOC register marker that should
-   have been eliminated, but may have crept back in.  */
+ *    have been eliminated, but may have crept back in.  */
 
 void
 rs6000_reorg (insn)
@@ -2540,7 +2427,7 @@ rs6000_reorg (insn)
 {
   if (flag_pic && (DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_SOLARIS))
     {
-      rtx got_reg = gen_rtx_REG (Pmode, GOT_TOC_REGNUM);
+      rtx got_reg = gen_rtx_REG (Pmode, 2);
       for ( ; insn != NULL_RTX; insn = NEXT_INSN (insn))
 	if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
 	    && reg_mentioned_p (got_reg, PATTERN (insn)))
@@ -2556,7 +2443,6 @@ struct machine_function
   int save_toc_p;
   int fpmem_size;
   int fpmem_offset;
-  rtx pic_offset_table_rtx;
 };
 
 /* Functions to save and restore rs6000_fpmem_size.
@@ -2574,7 +2460,6 @@ rs6000_save_machine_status (p)
   machine->sysv_varargs_p = rs6000_sysv_varargs_p;
   machine->fpmem_size     = rs6000_fpmem_size;
   machine->fpmem_offset   = rs6000_fpmem_offset;
-  machine->pic_offset_table_rtx = pic_offset_table_rtx;
 }
 
 void
@@ -2586,7 +2471,6 @@ rs6000_restore_machine_status (p)
   rs6000_sysv_varargs_p = machine->sysv_varargs_p;
   rs6000_fpmem_size     = machine->fpmem_size;
   rs6000_fpmem_offset   = machine->fpmem_offset;
-  pic_offset_table_rtx  = machine->pic_offset_table_rtx;
 
   free (machine);
   p->machine = (struct machine_function *)0;
@@ -2601,7 +2485,6 @@ rs6000_init_expanders ()
   rs6000_sysv_varargs_p = 0;
   rs6000_fpmem_size = 0;
   rs6000_fpmem_offset = 0;
-  pic_offset_table_rtx = (rtx)0;
 
   /* Arrange to save and restore machine status around nested functions.  */
   save_machine_status = rs6000_save_machine_status;
@@ -2646,7 +2529,7 @@ print_operand (file, x, code)
 
     case '*':
       /* Write the register number of the TOC register.  */
-      fputs (TARGET_MINIMAL_TOC ? reg_names[30] : reg_names[2], file);
+      fputs (TARGET_MINIMAL_TOC ? reg_names[30] : reg_names[2 /* PIC_OFFSET_TABLE_REGNUM? */ ], file);
       return;
 
     case '$':
@@ -3252,7 +3135,7 @@ print_operand_address (file, x)
 	;
 #endif
       else
-	fprintf (file, "(%s)", reg_names[ TARGET_MINIMAL_TOC ? 30 : 2 ]);
+	fprintf (file, "(%s)", reg_names[ TARGET_MINIMAL_TOC ? 30 : 2 /* PIC_OFFSET_TABLE_REGNUM? */ ]);
     }
   else if (GET_CODE (x) == PLUS && GET_CODE (XEXP (x, 1)) == REG)
     {
@@ -4119,8 +4037,28 @@ output_prolog (file, size)
       else
 	asm_fprintf (file, store_reg, reg_names[12], info->cr_save_offset + sp_offset,
 		     reg_names[sp_reg]);
+      /* we save all the condition registers as if they are a single 
+         register. The are physically, so this should work fine. */
+      if (dwarf2out_do_frame ())
+        {
+          SET_DWARF_LABEL (dw2_label);
+          dwarf2out_reg_save (dw2_label, 70, info->cr_save_offset);
+	}
     }
 
+  /* If we need PIC_OFFSET_TABLE_REGNUM, initialize it now */
+  if (TARGET_ELF && flag_pic == 1 && current_function_uses_pic_offset_table)
+    {
+      if (!info->lr_save_p)
+	asm_fprintf (file, "\tmflr %s\n", reg_names[0]);
+
+      fputs ("\tbl _GLOBAL_OFFSET_TABLE_@local-4\n", file);
+      asm_fprintf (file, "\tmflr %s\n", reg_names[PIC_OFFSET_TABLE_REGNUM]);
+
+      if (!info->lr_save_p)
+	asm_fprintf (file, "\tmtlr %s\n", reg_names[0]);
+    }
+
   /* NT needs us to probe the stack frame every 4k pages for large frames, so
      do it here.  */
   if (DEFAULT_ABI == ABI_NT && info->total_size > 4096)
Index: rs6000.h
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/config/rs6000/rs6000.h,v
retrieving revision 1.49
diff -u -p -r1.49 rs6000.h
--- rs6000.h	1999/05/13 12:38:42	1.49
+++ rs6000.h	1999/06/09 00:07:35
@@ -884,15 +919,18 @@ extern int rs6000_debug_arg;		/* debug a
    64-bit AIX reserves GPR13 for thread-private data.
    Conditionally disable FPRs.  */
 
-#define CONDITIONAL_REGISTER_USAGE	\
-{					\
-  if (! TARGET_POWER)			\
-    fixed_regs[64] = 1;			\
-  if (TARGET_64BIT)			\
-    fixed_regs[13] = call_used_regs[13] = 1; \
-  if (TARGET_SOFT_FLOAT)		\
-    for (i = 32; i < 64; i++)		\
-      fixed_regs[i] = call_used_regs[i] = 1; \
+#define CONDITIONAL_REGISTER_USAGE					\
+{									\
+  if (! TARGET_POWER)							\
+    fixed_regs[64] = 1;							\
+  if (TARGET_64BIT)							\
+    fixed_regs[13] = call_used_regs[13] = 1; 				\
+  if (TARGET_SOFT_FLOAT)						\
+    for (i = 32; i < 64; i++)						\
+      fixed_regs[i] = call_used_regs[i] = 1; 				\
+  if (TARGET_ELF && flag_pic == 1)					\
+    fixed_regs[PIC_OFFSET_TABLE_REGNUM]					\
+      = call_used_regs[PIC_OFFSET_TABLE_REGNUM] = 1;			\
 }
 
 /* Specify the registers used for certain standard purposes.
@@ -925,12 +963,6 @@ extern int rs6000_debug_arg;		/* debug a
 /* Special register that represents memory, used for float/int conversions.  */
 #define FPMEM_REGNUM 76
 
-/* Register to use as a placeholder for the GOT/allocated TOC register.
-   FINALIZE_PIC will change all uses of this register to a an appropriate
-   pseudo register when it adds the code to setup the GOT.  We use r2
-   because it is a reserved register in all of the ABI's.  */
-#define GOT_TOC_REGNUM 2
-
 /* Place that structure value return address is placed.
 
    On the RS/6000, it is passed as an extra parameter.  */
@@ -1146,12 +1178,21 @@ enum reg_class
 
    On the RS/6000, we have to return NO_REGS when we want to reload a
    floating-point CONST_DOUBLE to force it to be copied to memory.  */
-
+/*
 #define PREFERRED_RELOAD_CLASS(X,CLASS)			\
   ((GET_CODE (X) == CONST_DOUBLE			\
     && GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT)	\
    ? NO_REGS : (CLASS))
+*/
+#define PREFERRED_RELOAD_CLASS(X,CLASS)                \
+  (CONSTANT_P (X)                                      \
+   && ((CLASS) == FLOAT_REGS                           \
+       || (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \
+          && (HOST_FLOAT_FORMAT != IEEE_FLOAT_FORMAT   \
+              || HOST_BITS_PER_INT != BITS_PER_WORD))) \
+   ? NO_REGS : (CLASS))
 
+
 /* Return the register class of a scratch register needed to copy IN into
    or out of a register in CLASS in MODE.  If it can be done directly,
    NO_REGS is returned.  */
@@ -2105,7 +2151,7 @@ do {                                    
    this macro is not defined, it is up to the machine-dependent files
    to allocate such a register (if necessary).  */
 
-/* #define PIC_OFFSET_TABLE_REGNUM */
+#define PIC_OFFSET_TABLE_REGNUM 30
 
 /* Define this macro if the register defined by
    `PIC_OFFSET_TABLE_REGNUM' is clobbered by calls.  Do not define
@@ -2128,7 +2174,7 @@ do {                                    
    prologues being included in functions which used inline functions
    and were compiled to assembly language.)  */
 
-#define FINALIZE_PIC rs6000_finalize_pic ()
+/* #define FINALIZE_PIC */
 
 /* A C expression that is nonzero if X is a legitimate immediate
    operand on the target machine when generating position independent
@@ -2143,11 +2189,8 @@ do {                                    
 /* In rare cases, correct code generation requires extra machine
    dependent processing between the second jump optimization pass and
    delayed branch scheduling.  On those machines, define this macro
-   as a C statement to act on the code starting at INSN.
+   as a C statement to act on the code starting at INSN.  */
 
-   On the RS/6000, we use it to make sure the GOT_TOC register marker
-   that FINALIZE_PIC is supposed to remove actually got removed.  */
-
 #define MACHINE_DEPENDENT_REORG(INSN) rs6000_reorg (INSN)
 
 
Index: rs6000.md
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/config/rs6000/rs6000.md,v
retrieving revision 1.55
diff -u -p -r1.55 rs6000.md
--- rs6000.md	1999/05/13 12:38:44	1.55
+++ rs6000.md	1999/06/09 00:09:47
@@ -5809,21 +5809,6 @@
   "{l|lwz} %0,%a1@got(%2)"
   [(set_attr "type" "load")])
 
-;; Sometimes, though, the GOT `register' will be on the stack. Deal with
-;; this case specially.
-;; Force final to split this insn (if it hasn't been split already) to
-;; avoid having to create a suitable output template.
-(define_insn "*movsi_got_internal_mem"
-  [(set (match_operand:SI 0 "gpc_reg_operand" "=r")
-	(unspec [(match_operand:SI 1 "got_no_const_operand" "")
-		 (match_operand:SI 2 "memory_operand" "m")] 8))]
-  "(DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_SOLARIS)
-    && flag_pic == 1
-    && (reload_in_progress || reload_completed)"
-  "#"
-  [(set_attr "type" "load")
-   (set_attr "length" "8")])
-
 ;; Used by sched, shorten_branches and final when the GOT pseudo reg
 ;; didn't get allocated to a hard register.
 (define_split 
@@ -8327,16 +8312,6 @@
   [(unspec_volatile [(const_int 0)] 0)]
   ""
   "")
-
-;; V.4 specific code to initialize the PIC register
-
-(define_insn "init_v4_pic"
-  [(set (match_operand:SI 0 "register_operand" "=l")
-	(unspec [(const_int 0)] 7))]
-  "DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_SOLARIS"
-  "bl _GLOBAL_OFFSET_TABLE_@local-4"
-  [(set_attr "type" "branch")
-   (set_attr "length" "4")])
 
 
 ;; Compare insns are next.  Note that the RS/6000 has two types of compares,