[PATCH] middle-end: move initialization of stack_limit_rtx [PR103163]

[Sandra Loosemore <sandra@codesourcery.com>]

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This patch fixes the ICE I reported in PR103163.  We were initializing 
stack_limit_rtx before the register properties it depends on were 
getting set.  I moved it to the same function where stack_pointer_rtx, 
frame_pointer_rtx, etc are being initialized.

Besides nios2 where I observed it, this bug was also reported to affect 
powerpc.  Anybody want to check it there?  Otherwise, OK to check in?

-Sandra

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commit bd91ec874339f9fd256b2d83de7159f6c11f0000
Author: Sandra Loosemore <sandra@codesourcery.com>
Date:   Sat Jan 8 19:59:26 2022 -0800

    middle-end: move initialization of stack_limit_rtx [PR103163]
    
    stack_limit_rtx was being initialized before init_reg_modes_target (),
    resulting in the REG expression being created incorrectly and an ICE
    later in compilation.
    
    2022-01-08  Sandra Loosemore  <sandra@codesourcery.com>
    
    	PR middle-end/103163
    
    	gcc/
    	* emit-rtl.c (init_emit_regs): Initialize stack_limit_rtx here...
    	(init_emit_once): ...not here.

diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index feeee16..76dbe42 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -6097,6 +6097,13 @@ init_emit_regs (void)
   if ((unsigned) PIC_OFFSET_TABLE_REGNUM != INVALID_REGNUM)
     pic_offset_table_rtx = gen_raw_REG (Pmode, PIC_OFFSET_TABLE_REGNUM);
 
+  /* Process stack-limiting command-line options.  */
+  if (opt_fstack_limit_symbol_arg != NULL)
+    stack_limit_rtx
+      = gen_rtx_SYMBOL_REF (Pmode, ggc_strdup (opt_fstack_limit_symbol_arg));
+  if (opt_fstack_limit_register_no >= 0)
+    stack_limit_rtx = gen_rtx_REG (Pmode, opt_fstack_limit_register_no);
+
   for (i = 0; i < (int) MAX_MACHINE_MODE; i++)
     {
       mode = (machine_mode) i;
@@ -6177,13 +6184,6 @@ init_emit_once (void)
 
   /* Create the unique rtx's for certain rtx codes and operand values.  */
 
-  /* Process stack-limiting command-line options.  */
-  if (opt_fstack_limit_symbol_arg != NULL)
-    stack_limit_rtx 
-      = gen_rtx_SYMBOL_REF (Pmode, ggc_strdup (opt_fstack_limit_symbol_arg));
-  if (opt_fstack_limit_register_no >= 0)
-    stack_limit_rtx = gen_rtx_REG (Pmode, opt_fstack_limit_register_no);
-
   /* Don't use gen_rtx_CONST_INT here since gen_rtx_CONST_INT in this case
      tries to use these variables.  */
   for (i = - MAX_SAVED_CONST_INT; i <= MAX_SAVED_CONST_INT; i++)