This is a follow-up on bug 33291. It uses the same testcase (repeated here) but
with some additional optimization flags.
-------------------------------------------
struct Clock {
void f();
void add(unsigned n) { a += n; }
int a;
};
struct CPU : Clock {
virtual ~CPU();
unsigned char readSlow();
void execute();
void delay() { add(2); }
unsigned char readFast() {
if (unsigned char* p = ptrs[addr >> 8]) {
// fast-path
delay();
delay();
return p[addr & 255];
} else {
// slow-path
return readSlow();
}
}
typedef void (CPU::*FuncPtr)();
static FuncPtr tab[256];
unsigned char* ptrs[256];
unsigned addr;
};
void CPU::execute() {
f();
while (true) {
unsigned char b = readFast();
delay();
(this->*tab[b])();
}
}
----------------------------------------
When compiled with SVN revision 128074 on a linux x86_64 machine:
> g++ -O3 -fforce-addr -ftracer -S CPU.ii
> cat CPU.s
...
movl (%rbx), %eax
leal 4(%rax), %edx
addl $6, %eax
movl %edx, (%rbx) #### dead store
movzbl (%r12), %edx
movzbl (%rcx,%rdx), %edx
movl %eax, (%rbx)
...
--
Summary: follow-up on bug 33291 dead-store not eliminated
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: wouter dot vermaelen at scarlet dot be
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
