Mesa (master): intel/fs/gen12: Workaround data coherency issues due to broken NoMask control flow.
GitLab Mirror
gitlab-mirror at kemper.freedesktop.org
Fri Feb 14 22:36:08 UTC 2020
Module: Mesa
Branch: master
Commit: e14529ff3262a527d630cecac655f69c8ae15c3f
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=e14529ff3262a527d630cecac655f69c8ae15c3f
Author: Francisco Jerez <currojerez at riseup.net>
Date: Fri Jan 24 15:09:52 2020 -0800
intel/fs/gen12: Workaround data coherency issues due to broken NoMask control flow.
Together with the fixup_nomask_control_flow() pass introduced in a
previous patch, this implements a less invasive alternative to the
workaround documented in the hardware spec for GEN:BUG:1407528679,
which doesn't involve disabling structured control flow.
Under some conditions Gen12 hardware can end up executing a BB with
all channels disabled, which will lead to the execution of any NoMask
instructions in it, even though any execution-masked instructions will
be correctly shot down. This could break assumptions of the SWSB pass
if the data computed by a NoMask instruction is synchronized against
by using an SWSB annotation baked into a regular execution-masked
instruction, since the first (NoMask) instruction may be executed
redundantly by the hardware, even though the second will correctly be
shot down, potentially leading to a RaW or WaW hazard if a third
instruction subsequently accesses the destination register of the
first instruction.
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira at intel.com>
Cc: 20.0 <mesa-stable at lists.freedesktop.org>
---
src/intel/compiler/brw_fs_scoreboard.cpp | 134 +++++++++++++++++++++++--------
1 file changed, 100 insertions(+), 34 deletions(-)
diff --git a/src/intel/compiler/brw_fs_scoreboard.cpp b/src/intel/compiler/brw_fs_scoreboard.cpp
index 35586f2a107..5343aa1e634 100644
--- a/src/intel/compiler/brw_fs_scoreboard.cpp
+++ b/src/intel/compiler/brw_fs_scoreboard.cpp
@@ -281,21 +281,24 @@ namespace {
* No dependency information.
*/
dependency() : ordered(TGL_REGDIST_NULL), jp(INT_MIN),
- unordered(TGL_SBID_NULL), id(0) {}
+ unordered(TGL_SBID_NULL), id(0),
+ exec_all(false) {}
/**
* Construct a dependency on the in-order instruction with the provided
* ordered_address instruction counter.
*/
- dependency(tgl_regdist_mode mode, ordered_address jp) :
- ordered(mode), jp(jp), unordered(TGL_SBID_NULL), id(0) {}
+ dependency(tgl_regdist_mode mode, ordered_address jp, bool exec_all) :
+ ordered(mode), jp(jp), unordered(TGL_SBID_NULL), id(0),
+ exec_all(exec_all) {}
/**
* Construct a dependency on the out-of-order instruction with the
* specified synchronization token.
*/
- dependency(tgl_sbid_mode mode, unsigned id) :
- ordered(TGL_REGDIST_NULL), jp(INT_MIN), unordered(mode), id(id) {}
+ dependency(tgl_sbid_mode mode, unsigned id, bool exec_all) :
+ ordered(TGL_REGDIST_NULL), jp(INT_MIN), unordered(mode), id(id),
+ exec_all(exec_all) {}
/**
* Synchronization mode of in-order dependency, or zero if no in-order
@@ -327,6 +330,14 @@ namespace {
/** Synchronization token of out-of-order dependency. */
unsigned id;
+ /**
+ * Whether the dependency could be run with execution masking disabled,
+ * which might lead to the unwanted execution of the generating
+ * instruction in cases where a BB is executed with all channels
+ * disabled due to hardware bug GEN:BUG:1407528679.
+ */
+ bool exec_all;
+
/**
* Trivial in-order dependency that's always satisfied.
*
@@ -343,7 +354,8 @@ namespace {
return dep0.ordered == dep1.ordered &&
dep0.jp == dep1.jp &&
dep0.unordered == dep1.unordered &&
- dep0.id == dep1.id;
+ dep0.id == dep1.id &&
+ dep0.exec_all == dep1.exec_all;
}
friend bool
@@ -353,7 +365,7 @@ namespace {
}
};
- const dependency dependency::done = dependency(TGL_REGDIST_SRC, INT_MIN);
+ const dependency dependency::done = dependency(TGL_REGDIST_SRC, INT_MIN, false);
/**
* Return whether \p dep contains any dependency information.
@@ -388,6 +400,8 @@ namespace {
dep1.unordered ? dep1.id : dep0.id);
}
+ dep.exec_all = dep0.exec_all || dep1.exec_all;
+
return dep;
}
@@ -647,11 +661,22 @@ namespace {
if (dep.ordered && deps[i].ordered) {
deps[i].jp = MAX2(deps[i].jp, dep.jp);
deps[i].ordered |= dep.ordered;
+ deps[i].exec_all |= dep.exec_all;
dep.ordered = TGL_REGDIST_NULL;
}
- if (dep.unordered && deps[i].unordered && deps[i].id == dep.id) {
+ /* Don't combine otherwise matching unordered dependencies if
+ * there is an exec_all mismatch which would cause a SET
+ * dependency to gain an exec_all flag, since that would prevent
+ * it from being baked into the instruction we want to allocate an
+ * SBID for.
+ */
+ if (dep.unordered && deps[i].unordered && deps[i].id == dep.id &&
+ (deps[i].exec_all == dep.exec_all ||
+ (deps[i].exec_all && !(dep.unordered & TGL_SBID_SET)) ||
+ (dep.exec_all && !(deps[i].unordered & TGL_SBID_SET)))) {
deps[i].unordered |= dep.unordered;
+ deps[i].exec_all |= dep.exec_all;
dep.unordered = TGL_SBID_NULL;
}
}
@@ -664,17 +689,19 @@ namespace {
/**
* Construct a tgl_swsb annotation encoding any ordered dependencies from
- * the dependency list \p deps of an instruction with ordered_address
- * \p jp.
+ * the dependency list \p deps of an instruction with ordered_address \p
+ * jp. If \p exec_all is false only dependencies known to be executed with
+ * channel masking applied will be considered in the calculation.
*/
tgl_swsb
ordered_dependency_swsb(const dependency_list &deps,
- const ordered_address &jp)
+ const ordered_address &jp,
+ bool exec_all)
{
unsigned min_dist = ~0u;
for (unsigned i = 0; i < deps.size(); i++) {
- if (deps[i].ordered) {
+ if (deps[i].ordered && exec_all >= deps[i].exec_all) {
const unsigned dist = jp - deps[i].jp;
const unsigned max_dist = 10;
assert(jp > deps[i].jp);
@@ -688,27 +715,34 @@ namespace {
/**
* Return whether the dependency list \p deps of an instruction with
- * ordered_address \p jp has any non-trivial ordered dependencies.
+ * ordered_address \p jp has any non-trivial ordered dependencies. If \p
+ * exec_all is false only dependencies known to be executed with channel
+ * masking applied will be considered in the calculation.
*/
bool
find_ordered_dependency(const dependency_list &deps,
- const ordered_address &jp)
+ const ordered_address &jp,
+ bool exec_all)
{
- return ordered_dependency_swsb(deps, jp).regdist;
+ return ordered_dependency_swsb(deps, jp, exec_all).regdist;
}
/**
* Return the full tgl_sbid_mode bitset for the first unordered dependency
* on the list \p deps that matches the specified tgl_sbid_mode, or zero if
- * no such dependency is present.
+ * no such dependency is present. If \p exec_all is false only
+ * dependencies known to be executed with channel masking applied will be
+ * considered in the calculation.
*/
tgl_sbid_mode
find_unordered_dependency(const dependency_list &deps,
- tgl_sbid_mode unordered)
+ tgl_sbid_mode unordered,
+ bool exec_all)
{
if (unordered) {
for (unsigned i = 0; i < deps.size(); i++) {
- if (unordered & deps[i].unordered)
+ if ((unordered & deps[i].unordered) &&
+ exec_all >= deps[i].exec_all)
return deps[i].unordered;
}
}
@@ -727,17 +761,18 @@ namespace {
const dependency_list &deps,
const ordered_address &jp)
{
- const bool has_ordered = find_ordered_dependency(deps, jp);
+ const bool exec_all = inst->force_writemask_all;
+ const bool has_ordered = find_ordered_dependency(deps, jp, exec_all);
- if (find_unordered_dependency(deps, TGL_SBID_SET))
- return find_unordered_dependency(deps, TGL_SBID_SET);
+ if (find_unordered_dependency(deps, TGL_SBID_SET, exec_all))
+ return find_unordered_dependency(deps, TGL_SBID_SET, exec_all);
else if (has_ordered && is_unordered(inst))
return TGL_SBID_NULL;
- else if (find_unordered_dependency(deps, TGL_SBID_DST) &&
+ else if (find_unordered_dependency(deps, TGL_SBID_DST, exec_all) &&
(!has_ordered || !is_unordered(inst)))
- return find_unordered_dependency(deps, TGL_SBID_DST);
+ return find_unordered_dependency(deps, TGL_SBID_DST, exec_all);
else if (!has_ordered)
- return find_unordered_dependency(deps, TGL_SBID_SRC);
+ return find_unordered_dependency(deps, TGL_SBID_SRC, exec_all);
else
return TGL_SBID_NULL;
}
@@ -757,14 +792,17 @@ namespace {
update_inst_scoreboard(const fs_visitor *shader, const ordered_address *jps,
const fs_inst *inst, unsigned ip, scoreboard &sb)
{
+ const bool exec_all = inst->force_writemask_all;
+
/* Track any source registers that may be fetched asynchronously by this
* instruction, otherwise clear the dependency in order to avoid
* subsequent redundant synchronization.
*/
for (unsigned i = 0; i < inst->sources; i++) {
const dependency rd_dep =
- inst->is_payload(i) || inst->is_math() ? dependency(TGL_SBID_SRC, ip) :
- ordered_unit(inst) ? dependency(TGL_REGDIST_SRC, jps[ip]) :
+ (inst->is_payload(i) ||
+ inst->is_math()) ? dependency(TGL_SBID_SRC, ip, exec_all) :
+ ordered_unit(inst) ? dependency(TGL_REGDIST_SRC, jps[ip], exec_all) :
dependency::done;
for (unsigned j = 0; j < regs_read(inst, i); j++)
@@ -772,7 +810,7 @@ namespace {
}
if (is_send(inst) && inst->base_mrf != -1) {
- const dependency rd_dep = dependency(TGL_SBID_SRC, ip);
+ const dependency rd_dep = dependency(TGL_SBID_SRC, ip, exec_all);
for (unsigned j = 0; j < inst->mlen; j++)
sb.set(brw_uvec_mrf(8, inst->base_mrf + j, 0), rd_dep);
@@ -780,8 +818,8 @@ namespace {
/* Track any destination registers of this instruction. */
const dependency wr_dep =
- is_unordered(inst) ? dependency(TGL_SBID_DST, ip) :
- ordered_unit(inst) ? dependency(TGL_REGDIST_DST, jps[ip]) :
+ is_unordered(inst) ? dependency(TGL_SBID_DST, ip, exec_all) :
+ ordered_unit(inst) ? dependency(TGL_REGDIST_DST, jps[ip], exec_all) :
dependency();
if (is_valid(wr_dep) && inst->dst.file != BAD_FILE &&
@@ -870,6 +908,7 @@ namespace {
unsigned ip = 0;
foreach_block_and_inst(block, fs_inst, inst, shader->cfg) {
+ const bool exec_all = inst->force_writemask_all;
scoreboard &sb = sbs[block->num];
for (unsigned i = 0; i < inst->sources; i++) {
@@ -885,7 +924,8 @@ namespace {
}
if (is_unordered(inst))
- add_dependency(ids, deps[ip], dependency(TGL_SBID_SET, ip));
+ add_dependency(ids, deps[ip],
+ dependency(TGL_SBID_SET, ip, exec_all));
if (!inst->no_dd_check) {
if (inst->dst.file != BAD_FILE && !inst->dst.is_null()) {
@@ -967,7 +1007,8 @@ namespace {
unsigned ip = 0;
foreach_block_and_inst_safe(block, fs_inst, inst, shader->cfg) {
- tgl_swsb swsb = ordered_dependency_swsb(deps[ip], jps[ip]);
+ const bool exec_all = inst->force_writemask_all;
+ tgl_swsb swsb = ordered_dependency_swsb(deps[ip], jps[ip], exec_all);
const tgl_sbid_mode unordered_mode =
baked_unordered_dependency_mode(inst, deps[ip], jps[ip]);
@@ -975,9 +1016,13 @@ namespace {
const dependency &dep = deps[ip][i];
if (dep.unordered) {
- if (unordered_mode == dep.unordered && !swsb.mode) {
+ if (unordered_mode == dep.unordered &&
+ exec_all >= dep.exec_all && !swsb.mode) {
/* Bake unordered dependency into the instruction's SWSB if
- * possible.
+ * possible, except in cases where the current instruction
+ * isn't marked NoMask but the dependency is, since that
+ * might lead to data coherency issues due to
+ * GEN:BUG:1407528679.
*/
swsb.sbid = dep.id;
swsb.mode = dep.unordered;
@@ -986,7 +1031,7 @@ namespace {
* instruction.
*/
const fs_builder ibld = fs_builder(shader, block, inst)
- .exec_all().group(1, 0);
+ .exec_all().group(1, 0);
fs_inst *sync = ibld.emit(BRW_OPCODE_SYNC, ibld.null_reg_ud(),
brw_imm_ud(TGL_SYNC_NOP));
sync->sched.sbid = dep.id;
@@ -996,6 +1041,27 @@ namespace {
}
}
+ for (unsigned i = 0; i < deps[ip].size(); i++) {
+ const dependency &dep = deps[ip][i];
+
+ if (dep.ordered && dep.exec_all > exec_all &&
+ find_ordered_dependency(deps[ip], jps[ip], true)) {
+ /* If the current instruction is not marked NoMask but an
+ * ordered dependency is, perform the synchronization as a
+ * separate NoMask SYNC instruction in order to avoid data
+ * coherency issues due to GEN:BUG:1407528679. The similar
+ * scenario with unordered dependencies should have been
+ * handled above.
+ */
+ const fs_builder ibld = fs_builder(shader, block, inst)
+ .exec_all().group(1, 0);
+ fs_inst *sync = ibld.emit(BRW_OPCODE_SYNC, ibld.null_reg_ud(),
+ brw_imm_ud(TGL_SYNC_NOP));
+ sync->sched = ordered_dependency_swsb(deps[ip], jps[ip], true);
+ break;
+ }
+ }
+
/* Update the IR. */
inst->sched = swsb;
inst->no_dd_check = inst->no_dd_clear = false;
More information about the mesa-commit
mailing list