Paolo Bonzini <[EMAIL PROTECTED]> writes:
>> would in some cases be accurate.)  I think using an unspec in rs6000
>> would solve some of the port-specific issues.  In particular, I don't
>> think 36090 would have happened with an unspec representation.
>
> I agree.  So your plan would be to change rs6000 to an unspec, and drop
> the problematic hunk in simplify-rtx.c?  That would be okay with me, but
> it's not a small change for rs6000.

Yeah, this is very much my preferred option.

FWIW, here's a proof-of-concept patch for GNU/Linux and AIX.
It knowingly breaks Darwin, so it can't be applied as-is.
But if the idea seems OK to David, I'll volunteer to do the
Darwin stuff too (including x86 if necessary).

I compared the gcc.c-torture, gcc.dg and g++.dg output for the
following options:

    -O2
    -O2 -fpic
    -O2 -fPIC
    -O2 -mminimal-toc

on the following targets:

    powerpc-linux-gnu
    powerpc64-linux-gnu
    powerpc-aix4.3

and there were no differences.  diffstat says:

 4 files changed, 49 insertions(+), 81 deletions(-)

Richard


gcc/
        * config/rs6000/rs6000-protos.h (rs6000_output_addr_const_extra):
        Declare.
        * config/rs6000/rs6000.h (OUTPUT_ADDR_CONST_EXTRA): New macro.
        * config/rs6000/rs6000.md (UNSPEC_TOCREL): New constant.
        * config/rs6000/rs6000.c (constant_pool_expr_1): Delete.
        (constant_pool_expr_p): Use split_const and check the base.
        (toc_relative_expr_p): Likewise, checking for an UNSPEC_TOCREL
        instead of a MINUS.
        (legitimate_constant_pool_address_p): Check toc_relative_p
        instead of constant_pool_expr_p.
        (print_operand_address): Always use output_addr_const for
        constant pool addresses.
        (rs6000_output_addr_const_extra): New function.
        (create_TOC_reference): Create an UNSPEC_TOCREL instead of
        a MINUS.

Index: gcc/config/rs6000/rs6000-protos.h
===================================================================
--- gcc/config/rs6000/rs6000-protos.h   2008-09-07 11:22:24.000000000 +0100
+++ gcc/config/rs6000/rs6000-protos.h   2008-09-07 12:32:01.000000000 +0100
@@ -77,6 +77,7 @@ extern int extract_ME (rtx);
 extern void rs6000_output_function_entry (FILE *, const char *);
 extern void print_operand (FILE *, rtx, int);
 extern void print_operand_address (FILE *, rtx);
+extern bool rs6000_output_addr_const_extra (FILE *, rtx);
 extern enum rtx_code rs6000_reverse_condition (enum machine_mode,
                                               enum rtx_code);
 extern void rs6000_emit_sCOND (enum rtx_code, rtx);
Index: gcc/config/rs6000/rs6000.h
===================================================================
--- gcc/config/rs6000/rs6000.h  2008-09-07 11:20:37.000000000 +0100
+++ gcc/config/rs6000/rs6000.h  2008-09-07 12:31:43.000000000 +0100
@@ -2344,6 +2344,12 @@ #define PRINT_OPERAND_PUNCT_VALID_P(CODE
 
 #define PRINT_OPERAND_ADDRESS(FILE, ADDR) print_operand_address (FILE, ADDR)
 
+#define OUTPUT_ADDR_CONST_EXTRA(STREAM, X, FAIL)               \
+  do                                                           \
+    if (!rs6000_output_addr_const_extra (STREAM, X))           \
+      goto FAIL;                                               \
+  while (0)
+
 /* uncomment for disabling the corresponding default options */
 /* #define  MACHINE_no_sched_interblock */
 /* #define  MACHINE_no_sched_speculative */
Index: gcc/config/rs6000/rs6000.md
===================================================================
--- gcc/config/rs6000/rs6000.md 2008-09-07 11:13:27.000000000 +0100
+++ gcc/config/rs6000/rs6000.md 2008-09-07 12:02:53.000000000 +0100
@@ -99,6 +99,7 @@ (define_constants
    (UNSPEC_DLMZB_CR            46)
    (UNSPEC_DLMZB_STRLEN                47)
    (UNSPEC_RSQRT               48)
+   (UNSPEC_TOCREL              49)
   ])
 
 ;;
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c  2008-09-07 10:53:53.000000000 +0100
+++ gcc/config/rs6000/rs6000.c  2008-09-07 16:17:05.000000000 +0100
@@ -765,7 +765,6 @@ static void rs6000_emit_allocate_stack (
 static unsigned rs6000_hash_constant (rtx);
 static unsigned toc_hash_function (const void *);
 static int toc_hash_eq (const void *, const void *);
-static int constant_pool_expr_1 (rtx, int *, int *);
 static bool constant_pool_expr_p (rtx);
 static bool legitimate_small_data_p (enum machine_mode, rtx);
 static bool legitimate_lo_sum_address_p (enum machine_mode, rtx, int);
@@ -3456,58 +3455,28 @@ gpr_or_gpr_p (rtx op0, rtx op1)
 
 /* Subroutines of rs6000_legitimize_address and rs6000_legitimate_address.  */
 
-static int
-constant_pool_expr_1 (rtx op, int *have_sym, int *have_toc)
-{
-  switch (GET_CODE (op))
-    {
-    case SYMBOL_REF:
-      if (RS6000_SYMBOL_REF_TLS_P (op))
-       return 0;
-      else if (CONSTANT_POOL_ADDRESS_P (op))
-       {
-         if (ASM_OUTPUT_SPECIAL_POOL_ENTRY_P (get_pool_constant (op), Pmode))
-           {
-             *have_sym = 1;
-             return 1;
-           }
-         else
-           return 0;
-       }
-      else if (! strcmp (XSTR (op, 0), toc_label_name))
-       {
-         *have_toc = 1;
-         return 1;
-       }
-      else
-       return 0;
-    case PLUS:
-    case MINUS:
-      return (constant_pool_expr_1 (XEXP (op, 0), have_sym, have_toc)
-             && constant_pool_expr_1 (XEXP (op, 1), have_sym, have_toc));
-    case CONST:
-      return constant_pool_expr_1 (XEXP (op, 0), have_sym, have_toc);
-    case CONST_INT:
-      return 1;
-    default:
-      return 0;
-    }
-}
-
 static bool
 constant_pool_expr_p (rtx op)
 {
-  int have_sym = 0;
-  int have_toc = 0;
-  return constant_pool_expr_1 (op, &have_sym, &have_toc) && have_sym;
+  rtx base, offset;
+
+  split_const (op, &base, &offset);
+  return (GET_CODE (base) == SYMBOL_REF
+         && CONSTANT_POOL_ADDRESS_P (base)
+         && ASM_OUTPUT_SPECIAL_POOL_ENTRY_P (get_pool_constant (base), Pmode));
 }
 
 bool
 toc_relative_expr_p (rtx op)
 {
-  int have_sym = 0;
-  int have_toc = 0;
-  return constant_pool_expr_1 (op, &have_sym, &have_toc) && have_toc;
+  rtx base, offset;
+
+  if (!CONSTANT_P (op))
+    return false;
+
+  split_const (op, &base, &offset);
+  return (GET_CODE (base) == UNSPEC
+         && XINT (base, 1) == UNSPEC_TOCREL);
 }
 
 bool
@@ -3517,7 +3486,7 @@ legitimate_constant_pool_address_p (rtx 
          && GET_CODE (x) == PLUS
          && GET_CODE (XEXP (x, 0)) == REG
          && (TARGET_MINIMAL_TOC || REGNO (XEXP (x, 0)) == TOC_REGISTER)
-         && constant_pool_expr_p (XEXP (x, 1)));
+         && toc_relative_expr_p (XEXP (x, 1)));
 }
 
 static bool
@@ -12465,45 +12434,37 @@ print_operand_address (FILE *file, rtx x
 #endif
   else if (legitimate_constant_pool_address_p (x))
     {
-      if (TARGET_AIX && (!TARGET_ELF || !TARGET_MINIMAL_TOC))
-       {
-         rtx contains_minus = XEXP (x, 1);
-         rtx minus, symref;
-         const char *name;
-
-         /* Find the (minus (sym) (toc)) buried in X, and temporarily
-            turn it into (sym) for output_addr_const.  */
-         while (GET_CODE (XEXP (contains_minus, 0)) != MINUS)
-           contains_minus = XEXP (contains_minus, 0);
-
-         minus = XEXP (contains_minus, 0);
-         symref = XEXP (minus, 0);
-         gcc_assert (GET_CODE (XEXP (minus, 1)) == SYMBOL_REF);
-         XEXP (contains_minus, 0) = symref;
-         if (TARGET_ELF)
-           {
-             char *newname;
-
-             name = XSTR (symref, 0);
-             newname = XALLOCAVEC (char, strlen (name) + sizeof ("@toc"));
-             strcpy (newname, name);
-             strcat (newname, "@toc");
-             XSTR (symref, 0) = newname;
-           }
-         output_addr_const (file, XEXP (x, 1));
-         if (TARGET_ELF)
-           XSTR (symref, 0) = name;
-         XEXP (contains_minus, 0) = minus;
-       }
-      else
-       output_addr_const (file, XEXP (x, 1));
-
+      output_addr_const (file, XEXP (x, 1));
       fprintf (file, "(%s)", reg_names[REGNO (XEXP (x, 0))]);
     }
   else
     gcc_unreachable ();
 }
 
+/* Implement OUTPUT_ADDR_CONST_EXTRA for address X.  */
+
+bool
+rs6000_output_addr_const_extra (FILE *file, rtx x)
+{
+  if (GET_CODE (x) == UNSPEC)
+    switch (XINT (x, 1))
+      {
+      case UNSPEC_TOCREL:
+       x = XVECEXP (x, 0, 0);
+       gcc_assert (GET_CODE (x) == SYMBOL_REF);
+       output_addr_const (file, x);
+       if (!TARGET_AIX || (TARGET_ELF && TARGET_MINIMAL_TOC))
+         {
+           putc ('-', file);
+           assemble_name (file, toc_label_name);
+         }
+       else if (TARGET_ELF)
+         fputs ("@toc", file);
+       return true;
+      }
+  return false;
+}
+
 /* Target hook for assembling integer objects.  The PowerPC version has
    to handle fixup entries for relocatable code if RELOCATABLE_NEEDS_FIXUP
    is defined.  It also needs to handle DI-mode objects on 64-bit
@@ -15322,8 +15283,7 @@ create_TOC_reference (rtx symbol)
   return gen_rtx_PLUS (Pmode,
           gen_rtx_REG (Pmode, TOC_REGISTER),
             gen_rtx_CONST (Pmode,
-              gen_rtx_MINUS (Pmode, symbol,
-                gen_rtx_SYMBOL_REF (Pmode, toc_label_name))));
+              gen_rtx_UNSPEC (Pmode, gen_rtvec (1, symbol), UNSPEC_TOCREL)));
 }
 
 /* If _Unwind_* has been called from within the same module,

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