Assembly output optimisations (was: PR 51094 - fprint_w() in output_addr_const() reinstated)

Hello list,

these clean-ups and minor speedups complete some TODOs and semi-finished 
changes I have gathered in the ELF backend. In a nutshell:

Fixed comment style, used INT_BITS_STRLEN_BOUND from gnulib to be future 
proof on integer representation string length, replaced long arguments in 
fast printing functions with HOST_WIDE_INT that is always a larger type 
(also asserted that), converted some never-negative ints to unsigned. 
Guarded the output.h:default_elf_asm_output_* declarations, mimicking 
varasm.c (I'm not exactly sure why this is guarded in the first place). 
Changed default_elf_asm_output_* to be clearer and faster, they now 
fwrite() line by line instead of putting char by char. Implemented fast 
octal output in default_elf_asm_output_*, this should give a good boost to 
-flto, but I haven't measured a big testcase for this one.

All in all I get a speed-up of ~30 M instr out of ~2 G instr, for -g3 
compilation of reload.c. Actually saving all the putc() calls gives more 
significant gain, but I lost a tiny bit because of converting [sf]print_* 
functions to HOST_WIDE_INT from long, for PR 51094. So on i586 which has 
HOST_WIDE_INT 8 byte wide, I can see slow calls to __u{div,mod}di3 taking 
place. I don't know whether there is a meaning in writing LEB128 values 
greater than 2^31 but I could change all that to HOST_WIDEST_FAST_INT if 
you think so.

Time savings are minor too, about 10 ms out of 0.85 s. Memory usage is the 
same. Bootstrapped on x86, no regressions for C,C++ testsuite.

Thanks Andreas, hp, Mike, for your comments. Mike I'd appreciate if you 
elaborated on how to speed-up sprint_uw_rev(), I don't think I understood 
what you have in mind.

Thanks,
Dimitris
2012-08-07 Dimitrios Apostolou <jimis@gmx.net>

	* final.c: Assert that HOST_WIDE_INT is at least as wide as long.
	(output_addr_const): Use fprint_w() instead of fprintf() when
	CONST_INT or CONST_FIXED.
	(_sprint_uw): New static function.
	(sprint_ul_rev): Change to:
	(_sprint_uw_rev): Accept HOST_WIDE_INT arg instead of
	long. Changed i to unsigned.
	(INT_BITS_STRLEN_BOUND): Copied from gnulib.
	(HOST_WIDE_INT_STRING_LEN): Define.
	(fprint_ul, sprint_ul): Change to:
	(fprint_uw, sprint_uw): Accept HOST_WIDE_INT arg instead of
	long. Changed counter variables to unsigned.
	(fprint_uw_hex): Renamed from fprint_whex
	* output.h (fprint_ul, sprint_ul): Remove declarations.
	(fprint_w, fprint_uw, sprint_uw): Declare.
	(default_elf_asm_output_limited_string)
	(default_elf_asm_output_ascii): wrap in #ifdef ELF_ASCII_ESCAPES
	(fprint_uw_hex): Renamed from fprint_whex
	* elfos.h (ASM_GENERATE_INTERNAL_LABEL): Use sprint_uw() instead
	of sprint_ul().
	(ASM_OUTPUT_ASCII): Removed questionmark at the end of macro.
	* i386.c (print_reg): Use fprint_uw() instead of fprint_ul().
	* dwarf2asm.c (asm_output_data_sleb128): Change fprintf() to
	fputs() plus fprint_w(). Change fputc() to putc() in hot path.
	(dw2_assemble_integer, dw2_asm_output_data)
	(dw2_asm_output_data_uleb128): fprint_whex() renamed to
	fprint_uw_hex().
	* dwarf2out.c (dwarf2out_source_line): Changed comment. Use
	fprint_uw() instead of fprint_ul().
	* varasm.c (_elf_escape_char): New static function that writes a
	char to a string according to ELF_ASCII_ESCAPES.
	(_elf_output_ascii_line): New static function that writes to file
	a single .ascii assembler declaration.
	(default_elf_asm_output_limited_string)
	(default_elf_asm_output_ascii): Rewrote functions so that they
	fwrite() a full assembler line instead of putting char by char.

Assembly output optimisations (was: PR 51094 - fprint_w() in output_addr_const() reinstated)

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