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i965/fs: Fix a bug in register coalesce

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This commit fixes a bug in register coalesce that happens when one register
is moved to another the proper number of times but the channels are
re-arranged.  When this happens, the previous code would happily coalesce
the registers regardless of the fact that the channel mappins were wrong.

Signed-off-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Jason Ekstrand 2014-09-16 16:34:23 -07:00
parent 16819b48ab
commit 27d7ef094a
1 changed files with 17 additions and 0 deletions
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17
src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
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@ -200,6 +200,16 @@ fs_visitor::register_coalesce()
channels_remaining -= inst->regs_written;
} else {
const int offset = inst->src[0].reg_offset;
if (mov[offset]) {
/* This is the second time that this offset in the register has
* been set. This means, in particular, that inst->dst was
* live before this instruction and that the live ranges of
* inst->dst and inst->src[0] overlap and we can't coalesce the
* two variables. Let's ensure that doesn't happen.
*/
channels_remaining = -1;
continue;
}
reg_to_offset[offset] = inst->dst.reg_offset;
if (inst->src[0].width == 16)
reg_to_offset[offset + 1] = inst->dst.reg_offset + 1;
@ -212,6 +222,13 @@ fs_visitor::register_coalesce()
bool can_coalesce = true;
for (int i = 0; i < src_size; i++) {
if (reg_to_offset[i] != reg_to_offset[0] + i) {
/* Registers are out-of-order. */
can_coalesce = false;
reg_from = -1;
break;
}
var_to[i] = live_intervals->var_from_vgrf[reg_to] + reg_to_offset[i];
var_from[i] = live_intervals->var_from_vgrf[reg_from] + i;