middle-end/6679: wrong code generated for dead code

[Volker Reichelt]

Hi,

the problem can be demonstrated with the following testcase:

--------------------------snip here-------------------------
bool foo (int i)
{
    switch (i)
    {
        case 0: return false;
        case 1: return false;
        case 2: return false;
        case 3: return false;
        case 4: return false;
    }

    return false;
}

int main() { return 0; }
--------------------------snip here-------------------------

Compiling this with gcc 3.1, 3.2 or the 3.2-branch on i686-pc-linux-gnu I get
the following error message:

/tmp/ccii3YKY.o: In function `foo(int)':
/tmp/ccii3YKY.o(.text+0x11): undefined reference to `.L8'
collect2: ld returned 1 exit status

The assembler code for the function "foo" is:

	.align 2
.globl _Z3fooi
	.type	_Z3fooi,@function
_Z3fooi:
.LFB1:
	pushl	%ebp
.LCFI0:
	movl	%esp, %ebp
.LCFI1:
	cmpl	$4, 8(%ebp)
	ja	.L1
	movl	8(%ebp), %eax
	sall	$2, %eax
	movl	.L8(%eax), %eax     <--------- !!!!!
.L1:
	movl	$0, %eax
	popl	%ebp
	ret
.LFE1:
.Lfe1:
	.size	_Z3fooi,.Lfe1-_Z3fooi

Note that the problem disappears with only four cases in the switch statement.

The problem doesn't arise on the main trunk, though.
Because this is a regression from 3.0.x, I rate the PR as "high priority".

Greetings,
Volker

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6679