Totally bogus string optimizations

[Bernd Schmidt]

I just found out that on ia64, the simple test program

#include <string.h>
char *p;
int main ()
{
  strcpy (p, "Foobar");
}

causes _horrendous_ assembly code to be generated.  Apparently, for a machine
that does not define _STRING_ARCH_unaligned, /usr/include/bits/string2.h
contains totally bogus code.

I've compiled this on i386 with 2.95.2 just to see whether this could be a
gcc code quality regression that has crept in since this release.  The result
is below, and you can see, it's definitely the strcpy macro that's broken,
and just by looking at the preprocessor output you can see why this sort of
nonsense is happening - we construct eight constant arrays and then use one
of them as the source of the copy.

My suggestion: don't try to "optimize" string functions.  Delete string2.h.
What's the point anyway?  The compiler should know how to do these
optimizations properly.  Besides, you'll save compile time because the
preprocessor and parser no longer have to evaluate the resulting monster
expressions.

Guess I'll be running my SPEC tests with -D__NO_STRING_INLINES from now.
Maybe even submit a gcc patch to put that in the specs file.  Grumble...


Bernd

	.file	"tst.c"
	.version	"01.01"
gcc2_compiled.:
.section	.rodata
.LC0:
	.string	"Foobar"
.text
	.align 4
.globl main
	.type	 main,@function
main:
	pushl %ebp
	movl p,%ecx
	movl %esp,%ebp
	subl $88,%esp
	movb $70,-56(%ebp)
	movb $111,-55(%ebp)
	movl -56(%ebp),%eax
	movw %ax,-44(%ebp)
	movb $70,-64(%ebp)
	movb $111,-63(%ebp)
	movb $111,-62(%ebp)
	movb $98,-61(%ebp)
	movl -64(%ebp),%eax
	movl %eax,-36(%ebp)
	movb $70,-72(%ebp)
	movb $111,-71(%ebp)
	movb $111,-70(%ebp)
	movb $98,-69(%ebp)
	movl -72(%ebp),%eax
	movb $97,-68(%ebp)
	movb $0,-67(%ebp)
	movl %eax,-28(%ebp)
	movl -68(%ebp),%eax
	movb $70,-80(%ebp)
	movb $111,-79(%ebp)
	movb $111,-78(%ebp)
	movb $98,-77(%ebp)
	movl -80(%ebp),%edx
	movb $0,-54(%ebp)
	movb $0,-42(%ebp)
	movb $0,-60(%ebp)
	movb $0,-32(%ebp)
	movw %ax,-24(%ebp)
	movb $97,-76(%ebp)
	movb $114,-75(%ebp)
	movb $0,-74(%ebp)
	movl %edx,-20(%ebp)
	movl -76(%ebp),%eax
	movw %ax,-16(%ebp)
	movb $0,-14(%ebp)
	movl %edx,(%ecx)
	movl -16(%ebp),%eax
	movw %ax,4(%ecx)
	movb -14(%ebp),%al
	movb %al,6(%ecx)
	movl %ebp,%esp
	popl %ebp
	ret
.Lfe1:
	.size	 main,.Lfe1-main
	.comm	p,4,4
	.ident	"GCC: (GNU) 2.95.2 19991024 (release)"