https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96482
--- Comment #14 from Martin Liška <marxin at gcc dot gnu.org> ---
So in ltrans we end up with:
addr_to_index (struct nir_builder * b, struct nir_ssa_def * addr,
nir_address_format addr_format)
{
unsigned int num_channels;
unsigned int swizzle[16];
unsigned int i;
struct nir_ssa_def * D.7072;
unsigned int c;
struct nir_ssa_def * _9;
<bb 2> [local count: 1073741824]:
if (addr_format_3(D) == 3)
goto <bb 3>; [20.24%]
else
goto <bb 4>; [79.76%]
<bb 3> [local count: 1073741824]:
c = 0;
_9 = nir_swizzle (b_5(D), addr_6(D), &c, 1);
c ={v} {CLOBBER};
return _9;
<bb 4> [count: 0]:
__builtin_unreachable ();
}
that's fine, in WPA we identified that possible values are 3 and 5.
However ./src/gallium/targets/dri/libgallium_dri.so.ltrans65.ltrans.129t.ccp3
optimizes that to:
Folding statement: if (addr_format_3(D) == 3)
which is likely CONSTANT
Folding predicate addr_format_3(D) == 3 to 0
Folded into: if (0 != 0)
which is wrong.
The following code is executed:
if (flag_tree_bit_ccp)
{
wide_int nonzero_bits = get_nonzero_bits (var);
tree value;
widest_int mask;
if (SSA_NAME_VAR (var)
&& TREE_CODE (SSA_NAME_VAR (var)) == PARM_DECL
&& ipcp_get_parm_bits (SSA_NAME_VAR (var), &value, &mask))
{
val.lattice_val = CONSTANT;
val.value = value;
val.mask = mask;
if (nonzero_bits != -1)
val.mask &= extend_mask (nonzero_bits,
TYPE_SIGN (TREE_TYPE (var)));
}
where range info for var is:
(gdb) p *ri
$2 = {
ints = {
m_precision = 32,
m_max_len = 1 '\001',
m_len = "\001\001\001",
m_val = {3}
}
}
(gdb) p nonzero_bits.dump()
[0x3], precision = 32
(gdb) p mask.dump()
[...,0x6], precision = 192
(gdb) p debug_tree(value)
<integer_cst 0x7ffff7268e10 type <enumeral_type 0x7ffff720e738
nir_address_format> constant 5>
So that's we saw in WPA. So far so good, but now these 2 pieces of information
are combined:
val.mask &= extend_mask (nonzero_bits,
TYPE_SIGN (TREE_TYPE (var)));
(gdb) p val.mask.dump()
[...,0x2], precision = 192
and folding happens :/
