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Re: gcc 2.95.2, bug in gcse?

To: Franz dot Sirl-kernel at lauterbach dot com
Subject: Re: gcc 2.95.2, bug in gcse?
From: "Martin v. Loewis" <martin at loewis dot home dot cs dot tu-berlin dot de>
Date: Sun, 12 Mar 2000 20:20:04 +0100
CC: vonbrand at sleipnir dot valparaiso dot cl, ghouston at arglist dot com, gcc-bugs at gcc dot gnu dot org
References: <200003121553.e2CFrsb18591@sleipnir.valparaiso.cl> <200003121832.TAA00994@loewis.home.cs.tu-berlin.de> <00031220065200.00752@enzo.bigblue.local>

> The current gcc-2_95-branch works OK on powerpc-linux-gnu. Are you sure you
> didn't get confused by the strange testcase? It aborts for correct behaviour
> and segfaults for the bug.

Yes, here is the generated code

	.file	"a.c"
	.version	"01.01"
gcc2_compiled.:
.text
	.align 4
.globl main
	.type	 main,@function
main:
	pushl %ebp
	movl %esp,%ebp
	subl $8,%esp
	xorl %edx,%edx
	movb 0,%al
	.p2align 4,,7
.L6:
	testl %edx,%edx
	je .L4
	testb %al,%al
	je .L6
.L4:
	call abort
.Lfe1:
	.size	 main,.Lfe1-main
	.ident	"GCC: (GNU) 2.95.3 19991030 (prerelease)"

You'll notice the unconditional 
	movb 0,%al

which means 'al = *(char*)0'.

Regards,
Martin

References:
- Re: gcc 2.95.2, bug in gcse?
  - From: Horst von Brand
- Re: gcc 2.95.2, bug in gcse?
  - From: Martin v. Loewis
- Re: gcc 2.95.2, bug in gcse?
  - From: Franz Sirl

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