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Date: Wed, 14 Nov 2012 13:37:00 -0000
Message-ID: <CAF-06ZXmZ0uZxrghNRghRxnTAbYQDNirdb1CRqkz9LbERuzixA@mail.gmail.com>
Subject: pr26180.c
From: =?ISO-8859-1?Q?Andreas_Gei=DFler?= <setjem@googlemail.com>
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Hi.
I need your help again. I wrote my own backend for the gcc-4.6.2 and
it works nearly perfectly. But there is a problem with the test case
pr26180.c.
In this special case the register (r8), which is used for the
comparison, is not loaded. And i don't get why.

C-Code (pr26180.c):
...
x2 = ((x > 0)? (x): -(x));
...

Wrong translated assembler code:
...
        ;x > 0?
	cmpi.l	r8,-2147483648       <- r8 is not used in the hole function
and so it is not initialized with x
	jmp		C,_L2
	
xori.l	        r8,-1
	addi.l  	r8,1
_L2:
...

If i only change the comparison integer from 0 to 1 all works fine:

C-Code:
...
x2 = (x > 1 ? x : (-x));
...

Translated assembler code:
...
        ;load r8
	mov.l		r8,fp
	addi.l		r8,4
	mov.l		r9,r8
	ldr.l		r8,r9

        ;x > 1?
	cmpi.l	r8,-1
	jmpn		N,_L2

        ;x2 = -x
	mov.l		r8,fp
	addi.l		r8,4
	mov.l		r9,r8
	ldr.l		r8,r9
	xori.l		r8,-1
	addi.l		r8,1
	jmp		T,_L3
_L2:
        ;x2 = x
	mov.l		r8,fp
	addi.l		r8,4
	mov.l		r9,r8
	ldr.l		r8,r9
_L3:
...

So i you would like to ask you, which special pattern (machine
description pattern (*.md))
is related to "x2 = ((x > 0)? (x): -(x));" or where should i search the problem.