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.
---
src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
index a4abb88..51b482d 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp
@@ -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;
--
2.1.0
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