Change the hack to always apply, adjusting the register number
according to the dispatch_width.
The original change assumed that given for dispatch_width > 8 we
already prevent the overlap of source and destination for send, it
would not be necessary to explicitly add an interference with a
register that covers r127.
The problem is that the code for spilling registers ends up generating
scratch reads, that in Gen7+ will reuse the destination register,
causing a send with both source and destination overlaping. So prevent
r127 (or the overlapping wider register) to be used as destination for
sends.
This patch fixes piglit test
tests/spec/arb_compute_shader/linker/bug-93840.shader_test.
Fixes: 232ed898021 "i965/fs: Register allocator shoudn't use grf127 for sends
dest"
---
After more digging on the piglit failure, I came up with this
patch. I'm still seeing crashes with for some shader-db executions
(master have them too), but didn't have time today to drill into them.
src/intel/compiler/brw_fs_reg_allocate.cpp | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/src/intel/compiler/brw_fs_reg_allocate.cpp
b/src/intel/compiler/brw_fs_reg_allocate.cpp
index 59e047483c0..417ddeba09c 100644
--- a/src/intel/compiler/brw_fs_reg_allocate.cpp
+++ b/src/intel/compiler/brw_fs_reg_allocate.cpp
@@ -549,7 +549,7 @@ fs_visitor::assign_regs(bool allow_spilling, bool spill_all)
if (devinfo->gen >= 7)
node_count += BRW_MAX_GRF - GEN7_MRF_HACK_START;
int grf127_send_hack_node = node_count;
- if (devinfo->gen >= 8 && dispatch_width == 8)
+ if (devinfo->gen >= 8 && dispatch_width >= 8)
node_count ++;
struct ra_graph *g =
ra_alloc_interference_graph(compiler->fs_reg_sets[rsi].regs, node_count);
@@ -656,7 +656,7 @@ fs_visitor::assign_regs(bool allow_spilling, bool spill_all)
}
}
- if (devinfo->gen >= 8 && dispatch_width == 8) {
+ if (devinfo->gen >= 8 && dispatch_width >= 8) {
/* At Intel Broadwell PRM, vol 07, section "Instruction Set Reference",
* subsection "EUISA Instructions", Send Message (page 990):
*
@@ -665,12 +665,9 @@ fs_visitor::assign_regs(bool allow_spilling, bool
spill_all)
*
* We are avoiding using grf127 as part of the destination of send
* messages adding a node interference to the grf127_send_hack_node.
- * This node has a fixed asignment to grf127.
- *
- * We don't apply it to SIMD16 because previous code avoids any register
- * overlap between sources and destination.
+ * This node has a fixed assignment that overlaps with grf127.
*/
- ra_set_node_reg(g, grf127_send_hack_node, 127);
+ ra_set_node_reg(g, grf127_send_hack_node, 128 - reg_width);
foreach_block_and_inst(block, fs_inst, inst, cfg) {
if (inst->is_send_from_grf() && inst->dst.file == VGRF) {
ra_add_node_interference(g, inst->dst.nr, grf127_send_hack_node);
--
2.18.0
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