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Re: detailed comparison of generated code size for GCC and other compilers
Optimizations based on uninitialized variables make me very nervous.
If uninitialized memory reads are transformed into don't-cares, then
checking tools like valgrind will no longer see the UMR (assuming that
the lack of initialization is a bug).
Did I understand that icc does this? It seems like a dangerous practice.
Yes, it looks like icc does this. But so does gcc, see below. There is
no "add" in the generated code.
John Regehr
[regehr@babel ~]$ cat undef.c
int foo (int x)
{
int y;
return x+y;
}
[regehr@babel ~]$ current-gcc -O3 -S -o - undef.c -fomit-frame-pointer
.file "undef.c"
.text
.p2align 4,,15
.globl foo
.type foo, @function
foo:
movl 4(%esp), %eax
ret
.size foo, .-foo
.ident "GCC: (GNU) 4.5.0 20091117 (experimental)"
.section .note.GNU-stack,"",@progbits