[FT32] : apply unbias to references to RAM symbols

The FT32 binutils use a bias to distinguish between RAM and flash
addresses.

This fix adds an ASM_OUTPUT_SYMBOL_REF() that unbiases references to
RAM symbols.

Only references to RAM objects have the bias applied. Flash objects
(that is, objects in ADDR SPACE 1) are not biased, so for these no bias
should be applied. Likewise references in the gdb section need to use
the biased address, so references in debug sections are not unbiased.

gcc/ChangeLog:

2016-07-08  James Bowman  <james.bowman@ftdichip.com>

	* config/ft32/ft32.c (ft32_elf_encode_section_info): New function.
	* config/ft32/ft32.h (ASM_OUTPUT_SYMBOL_REF): New function.

James Bowman schrieb:
> The FT32 binutils use a bias to distinguish between RAM and flash
> addresses.
> 
> This fix adds an ASM_OUTPUT_SYMBOL_REF() that unbiases references to
> RAM symbols.
> 
> Only references to RAM objects have the bias applied. Flash objects
> (that is, objects in ADDR SPACE 1) are not biased, so for these no bias
> should be applied. Likewise references in the gdb section need to use
> the biased address, so references in debug sections are not unbiased.
> 
> gcc/ChangeLog:
> 
> 2016-07-08  James Bowman  <james.bowman@ftdichip.com>
> 
> 	* config/ft32/ft32.c (ft32_elf_encode_section_info): New function.
> 	* config/ft32/ft32.h (ASM_OUTPUT_SYMBOL_REF): New function.

Huh, ASM_OUTPUT_SYMBOL_REF it's a macro.

> 
> Index: gcc/config/ft32/ft32.c
> ===================================================================
> --- gcc/config/ft32/ft32.c	(revision 237998)
> +++ gcc/config/ft32/ft32.c	(working copy)
> @@ -35,6 +35,7 @@
>  #include "calls.h"
>  #include "expr.h"
>  #include "builtins.h"
> +#include "print-tree.h"

Seems this include is no more needed as you commented-out below the used 
functions.  If the header is actually needed it should be mentioned in 
the ChangeLog.

>  /* This file should be included last.  */
>  #include "target-def.h"
> @@ -895,6 +896,46 @@ yes:
>    return 1;
>  }
>  
> +#undef TARGET_ENCODE_SECTION_INFO
> +#define TARGET_ENCODE_SECTION_INFO  ft32_elf_encode_section_info
> +
> +void
> +ft32_elf_encode_section_info (tree decl, rtx rtl, int first)

Can't this function be static?

> +{
> +  enum tree_code code;
> +  rtx symbol;
> +
> +  /* Careful not to prod global register variables.  */
> +  if (!MEM_P (rtl))
> +    return;
> +  symbol = XEXP (rtl, 0);
> +  if (GET_CODE (symbol) != SYMBOL_REF)

We have SYMBOL_REF_P ==> if (!SYMBOL_REF_P (symbol)) ...

> +    return;
> +
> +  default_encode_section_info (decl, rtl, first);
> +
> +  code = TREE_CODE (decl);
> +  switch (TREE_CODE_CLASS (code))
> +    {
> +    case tcc_declaration:
> +      {
> +	tree type = TREE_TYPE (decl);
> +	int is_flash = (type && TYPE_P (type) && !ADDR_SPACE_GENERIC_P (TYPE_ADDR_SPACE (type)));

Line too long, should be wrapped, e.g. before the "&&".

> +	if ((code == VAR_DECL) && !is_flash)
> +	  SYMBOL_REF_FLAGS (symbol) |= 0x1000;

"0x1000" is fragile.  If rtl.h::SYMBOL_FLAG_MACH_DEP_SHIFT is bumped in 
a future version because generic symbol_ref flags are added, hard-coded 
flags like these will break your code.

> +      }
> +      break;
> +    case tcc_constant:
> +    case tcc_exceptional:
> +      if (code == STRING_CST)
> +	SYMBOL_REF_FLAGS (symbol) |= 0x1000;

Same here.

> +    }
> +
> +  // debug_tree (decl);
> +  // debug_rtx (rtl);
> +  // printf("\n");

No code in comments.

> +}
> +
>  struct gcc_target targetm = TARGET_INITIALIZER;
>  
>  #include "gt-ft32.h"
> Index: gcc/config/ft32/ft32.h
> ===================================================================
> --- gcc/config/ft32/ft32.h	(revision 237998)
> +++ gcc/config/ft32/ft32.h	(working copy)
> @@ -506,4 +506,14 @@ do { \
>  
>  extern int ft32_is_mem_pm(rtx o);

Such prototypes usually live in ft32-protos.h, not in ft32.h.

>  
> +#define ASM_OUTPUT_SYMBOL_REF(stream, sym) \
> +  do { \
> +    assemble_name (stream, XSTR (sym, 0)); \
> +    int section_debug = in_section && \
> +      (SECTION_STYLE (in_section) == SECTION_NAMED) && \

If lines are wrapped, then before operators like "&&", not after them.

> +      (in_section->named.common.flags & SECTION_DEBUG); \
> +    if (!section_debug && SYMBOL_REF_FLAGS (sym) & 0x1000) \

Same here with magic "0x1000".

> +      asm_fprintf (stream, "-0x800000"); \
> +  } while (0)
> +
>  #endif /* GCC_FT32_H */

Johann