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Revision a90b1e32d2f697d1aa39b49038469e2ea40d5e7b authored by Adam Langley on 03 June 2013, 19:45:11 UTC, committed by Emilia Kasper on 19 August 2014, 15:09:27 UTC
Add volatile qualifications to two blocks of inline asm to stop GCC from
eliminating them as dead code.

Both volatile and "memory" are used because of some concern that the compiler
may still cache values across the asm block without it, and because this was
such a painful debugging session that I wanted to ensure that it's never
repeated.

(cherry picked from commit 7753a3a68431aa81b82beea4c3f5374b41454679)

Conflicts:
	crypto/bn/asm/x86_64-gcc.c

Reviewed-by: Rich Salz <rsalz@openssl.org>
1 parent 0ed8e95
Raw File
sgiccbug.c
/* NOCW */
/* sgibug.c */
/* bug found by Eric Young (eay@mincom.oz.au) May 95 */

#include <stdio.h>

/* This compiler bug it present on IRIX 5.3, 5.1 and 4.0.5 (these are
 * the only versions of IRIX I have access to.
 * defining FIXBUG removes the bug.
 * (bug is still present in IRIX 6.3 according to
 * Gage <agage@forgetmenot.Mines.EDU>
 */
 
/* Compare the output from
 * cc sgiccbug.c; ./a.out
 * and
 * cc -O sgiccbug.c; ./a.out
 */

static unsigned long a[4]={0x01234567,0x89ABCDEF,0xFEDCBA98,0x76543210};
static unsigned long b[4]={0x89ABCDEF,0xFEDCBA98,0x76543210,0x01234567};
static unsigned long c[4]={0x77777778,0x8ACF1357,0x88888888,0x7530ECA9};

main()
	{
	unsigned long r[4];
	sub(r,a,b);
	fprintf(stderr,"input a= %08X %08X %08X %08X\n",a[3],a[2],a[1],a[0]);
	fprintf(stderr,"input b= %08X %08X %08X %08X\n",b[3],b[2],b[1],b[0]);
	fprintf(stderr,"output = %08X %08X %08X %08X\n",r[3],r[2],r[1],r[0]);
	fprintf(stderr,"correct= %08X %08X %08X %08X\n",c[3],c[2],c[1],c[0]);
	}

int sub(r,a,b)
unsigned long *r,*a,*b;
	{
	register unsigned long t1,t2,*ap,*bp,*rp;
	int i,carry;
#ifdef FIXBUG
	unsigned long dummy;
#endif

	ap=a;
	bp=b;
	rp=r;
	carry=0;
	for (i=0; i<4; i++)
		{
		t1= *(ap++);
		t2= *(bp++);
		t1=(t1-t2);
#ifdef FIXBUG
		dummy=t1;
#endif
		*(rp++)=t1&0xffffffff;
		}
	}
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