* exists and therefore remove the instruction.
*/
+using namespace brw;
+
static bool
cmod_propagate_cmp_to_add(const gen_device_info *devinfo, bblock_t *block,
fs_inst *inst)
{
bool read_flag = false;
+ const unsigned flags_written = inst->flags_written();
foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst) {
if (scan_inst->opcode == BRW_OPCODE_ADD &&
goto not_match;
}
- /* From the Sky Lake PRM Vol. 7 "Assigning Conditional Mods":
+ /* If the scan instruction writes a different flag register than the
+ * instruction we're trying to propagate from, bail.
+ *
+ * FINISHME: The second part of the condition may be too strong.
+ * Perhaps (scan_inst->flags_written() & flags_written) !=
+ * flags_written?
+ */
+ if (scan_inst->flags_written() != 0 &&
+ scan_inst->flags_written() != flags_written)
+ goto not_match;
+
+ /* From the Kaby Lake PRM Vol. 7 "Assigning Conditional Flags":
*
* * Note that the [post condition signal] bits generated at
* the output of a compute are before the .sat.
*
- * So we don't have to bail if scan_inst has saturate.
+ * Paragraph about post_zero does not mention saturation, but
+ * testing it on actual GPUs shows that conditional modifiers
+ * are applied after saturation.
+ *
+ * * post_zero bit: This bit reflects whether the final
+ * result is zero after all the clamping, normalizing,
+ * or format conversion logic.
+ *
+ * For signed types we don't care about saturation: it won't
+ * change the result of conditional modifier.
+ *
+ * For floating and unsigned types there two special cases,
+ * when we can remove inst even if scan_inst is saturated: G
+ * and LE. Since conditional modifiers are just comparations
+ * against zero, saturating positive values to the upper
+ * limit never changes the result of comparation.
+ *
+ * For negative values:
+ * (sat(x) > 0) == (x > 0) --- false
+ * (sat(x) <= 0) == (x <= 0) --- true
*/
- /* Otherwise, try propagating the conditional. */
const enum brw_conditional_mod cond =
negate ? brw_swap_cmod(inst->conditional_mod)
: inst->conditional_mod;
+ if (scan_inst->saturate &&
+ (brw_reg_type_is_floating_point(scan_inst->dst.type) ||
+ type_is_unsigned_int(scan_inst->dst.type)) &&
+ (cond != BRW_CONDITIONAL_G &&
+ cond != BRW_CONDITIONAL_LE))
+ goto not_match;
+
+ /* Otherwise, try propagating the conditional. */
if (scan_inst->can_do_cmod() &&
((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) ||
scan_inst->conditional_mod == cond)) {
}
not_match:
- if (scan_inst->flags_written())
+ if ((scan_inst->flags_written() & flags_written) != 0)
+ break;
+
+ read_flag = read_flag ||
+ (scan_inst->flags_read(devinfo) & flags_written) != 0;
+ }
+
+ return false;
+}
+
+/**
+ * Propagate conditional modifiers from NOT instructions
+ *
+ * Attempt to convert sequences like
+ *
+ * or(8) g78<8,8,1> g76<8,8,1>UD g77<8,8,1>UD
+ * ...
+ * not.nz.f0(8) null g78<8,8,1>UD
+ *
+ * into
+ *
+ * or.z.f0(8) g78<8,8,1> g76<8,8,1>UD g77<8,8,1>UD
+ */
+static bool
+cmod_propagate_not(const gen_device_info *devinfo, bblock_t *block,
+ fs_inst *inst)
+{
+ const enum brw_conditional_mod cond = brw_negate_cmod(inst->conditional_mod);
+ bool read_flag = false;
+ const unsigned flags_written = inst->flags_written();
+
+ if (cond != BRW_CONDITIONAL_Z && cond != BRW_CONDITIONAL_NZ)
+ return false;
+
+ foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst) {
+ if (regions_overlap(scan_inst->dst, scan_inst->size_written,
+ inst->src[0], inst->size_read(0))) {
+ if (scan_inst->opcode != BRW_OPCODE_OR &&
+ scan_inst->opcode != BRW_OPCODE_AND)
+ break;
+
+ if (scan_inst->is_partial_write() ||
+ scan_inst->dst.offset != inst->src[0].offset ||
+ scan_inst->exec_size != inst->exec_size)
+ break;
+
+ /* If the scan instruction writes a different flag register than the
+ * instruction we're trying to propagate from, bail.
+ *
+ * FINISHME: The second part of the condition may be too strong.
+ * Perhaps (scan_inst->flags_written() & flags_written) !=
+ * flags_written?
+ */
+ if (scan_inst->flags_written() != 0 &&
+ scan_inst->flags_written() != flags_written)
+ break;
+
+ if (scan_inst->can_do_cmod() &&
+ ((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) ||
+ scan_inst->conditional_mod == cond)) {
+ scan_inst->conditional_mod = cond;
+ inst->remove(block);
+ return true;
+ }
+ break;
+ }
+
+ if ((scan_inst->flags_written() & flags_written) != 0)
break;
- read_flag = read_flag || scan_inst->flags_read(devinfo);
+ read_flag = read_flag ||
+ (scan_inst->flags_read(devinfo) & flags_written) != 0;
}
return false;
if ((inst->opcode != BRW_OPCODE_AND &&
inst->opcode != BRW_OPCODE_CMP &&
- inst->opcode != BRW_OPCODE_MOV) ||
+ inst->opcode != BRW_OPCODE_MOV &&
+ inst->opcode != BRW_OPCODE_NOT) ||
inst->predicate != BRW_PREDICATE_NONE ||
!inst->dst.is_null() ||
(inst->src[0].file != VGRF && inst->src[0].file != ATTR &&
/* A CMP with a second source of zero can match with anything. A CMP
* with a second source that is not zero can only match with an ADD
* instruction.
+ *
+ * Only apply this optimization to float-point sources. It can fail for
+ * integers. For inputs a = 0x80000000, b = 4, int(0x80000000) < 4, but
+ * int(0x80000000) - 4 overflows and results in 0x7ffffffc. that's not
+ * less than zero, so the flags get set differently than for (a < b).
*/
if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero()) {
- progress = cmod_propagate_cmp_to_add(devinfo, block, inst) || progress;
+ if (brw_reg_type_is_floating_point(inst->src[0].type) &&
+ cmod_propagate_cmp_to_add(devinfo, block, inst))
+ progress = true;
+
+ continue;
+ }
+
+ if (inst->opcode == BRW_OPCODE_NOT) {
+ progress = cmod_propagate_not(devinfo, block, inst) || progress;
continue;
}
bool read_flag = false;
+ const unsigned flags_written = inst->flags_written();
foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst) {
if (regions_overlap(scan_inst->dst, scan_inst->size_written,
inst->src[0], inst->size_read(0))) {
+ /* If the scan instruction writes a different flag register than
+ * the instruction we're trying to propagate from, bail.
+ *
+ * FINISHME: The second part of the condition may be too strong.
+ * Perhaps (scan_inst->flags_written() & flags_written) !=
+ * flags_written?
+ */
+ if (scan_inst->flags_written() != 0 &&
+ scan_inst->flags_written() != flags_written)
+ break;
+
if (scan_inst->is_partial_write() ||
scan_inst->dst.offset != inst->src[0].offset ||
scan_inst->exec_size != inst->exec_size)
/* CMP's result is the same regardless of dest type. */
if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
scan_inst->opcode == BRW_OPCODE_CMP &&
- (inst->dst.type == BRW_REGISTER_TYPE_D ||
- inst->dst.type == BRW_REGISTER_TYPE_UD)) {
+ brw_reg_type_is_integer(inst->dst.type)) {
inst->remove(block);
progress = true;
break;
if (inst->opcode == BRW_OPCODE_AND)
break;
- /* Comparisons operate differently for ints and floats */
- if (scan_inst->dst.type != inst->dst.type &&
- (scan_inst->dst.type == BRW_REGISTER_TYPE_F ||
- inst->dst.type == BRW_REGISTER_TYPE_F))
+ /* Not safe to use inequality operators if the types are different
+ */
+ if (scan_inst->dst.type != inst->src[0].type &&
+ inst->conditional_mod != BRW_CONDITIONAL_Z &&
+ inst->conditional_mod != BRW_CONDITIONAL_NZ)
break;
- /* If the instruction generating inst's source also wrote the
- * flag, and inst is doing a simple .nz comparison, then inst
- * is redundant - the appropriate value is already in the flag
- * register. Delete inst.
+ /* Comparisons operate differently for ints and floats */
+ if (scan_inst->dst.type != inst->dst.type) {
+ /* Comparison result may be altered if the bit-size changes
+ * since that affects range, denorms, etc
+ */
+ if (type_sz(scan_inst->dst.type) != type_sz(inst->dst.type))
+ break;
+
+ /* We should propagate from a MOV to another instruction in a
+ * sequence like:
+ *
+ * and(16) g31<1>UD g20<8,8,1>UD g22<8,8,1>UD
+ * mov.nz.f0(16) null<1>F g31<8,8,1>D
+ */
+ if (inst->opcode == BRW_OPCODE_MOV) {
+ if ((inst->src[0].type != BRW_REGISTER_TYPE_D &&
+ inst->src[0].type != BRW_REGISTER_TYPE_UD) ||
+ (scan_inst->dst.type != BRW_REGISTER_TYPE_D &&
+ scan_inst->dst.type != BRW_REGISTER_TYPE_UD)) {
+ break;
+ }
+ } else if (brw_reg_type_is_floating_point(scan_inst->dst.type) !=
+ brw_reg_type_is_floating_point(inst->dst.type)) {
+ break;
+ }
+ }
+
+ /* Knowing following:
+ * - CMP writes to flag register the result of
+ * applying cmod to the `src0 - src1`.
+ * After that it stores the same value to dst.
+ * Other instructions first store their result to
+ * dst, and then store cmod(dst) to the flag
+ * register.
+ * - inst is either CMP or MOV
+ * - inst->dst is null
+ * - inst->src[0] overlaps with scan_inst->dst
+ * - inst->src[1] is zero
+ * - scan_inst wrote to a flag register
+ *
+ * There can be three possible paths:
+ *
+ * - scan_inst is CMP:
+ *
+ * Considering that src0 is either 0x0 (false),
+ * or 0xffffffff (true), and src1 is 0x0:
+ *
+ * - If inst's cmod is NZ, we can always remove
+ * scan_inst: NZ is invariant for false and true. This
+ * holds even if src0 is NaN: .nz is the only cmod,
+ * that returns true for NaN.
+ *
+ * - .g is invariant if src0 has a UD type
+ *
+ * - .l is invariant if src0 has a D type
+ *
+ * - scan_inst and inst have the same cmod:
+ *
+ * If scan_inst is anything than CMP, it already
+ * wrote the appropriate value to the flag register.
+ *
+ * - else:
+ *
+ * We can change cmod of scan_inst to that of inst,
+ * and remove inst. It is valid as long as we make
+ * sure that no instruction uses the flag register
+ * between scan_inst and inst.
*/
- if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
- !inst->src[0].negate &&
+ if (!inst->src[0].negate &&
scan_inst->flags_written()) {
- inst->remove(block);
- progress = true;
- break;
+ if (scan_inst->opcode == BRW_OPCODE_CMP) {
+ if ((inst->conditional_mod == BRW_CONDITIONAL_NZ) ||
+ (inst->conditional_mod == BRW_CONDITIONAL_G &&
+ inst->src[0].type == BRW_REGISTER_TYPE_UD) ||
+ (inst->conditional_mod == BRW_CONDITIONAL_L &&
+ inst->src[0].type == BRW_REGISTER_TYPE_D)) {
+ inst->remove(block);
+ progress = true;
+ break;
+ }
+ } else if (scan_inst->conditional_mod == inst->conditional_mod) {
+ inst->remove(block);
+ progress = true;
+ break;
+ } else if (!read_flag) {
+ scan_inst->conditional_mod = inst->conditional_mod;
+ inst->remove(block);
+ progress = true;
+ break;
+ }
}
/* The conditional mod of the CMP/CMPN instructions behaves
scan_inst->opcode == BRW_OPCODE_CMPN)
break;
- /* From the Sky Lake PRM Vol. 7 "Assigning Conditional Mods":
- *
- * * Note that the [post condition signal] bits generated at
- * the output of a compute are before the .sat.
- */
- if (scan_inst->saturate)
- break;
-
/* From the Sky Lake PRM, Vol 2a, "Multiply":
*
* "When multiplying integer data types, if one of the sources
scan_inst->opcode == BRW_OPCODE_MUL)
break;
- /* Otherwise, try propagating the conditional. */
enum brw_conditional_mod cond =
inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod)
: inst->conditional_mod;
+ /* From the Sky Lake PRM Vol. 7 "Assigning Conditional Mods":
+ *
+ * * Note that the [post condition signal] bits generated at
+ * the output of a compute are before the .sat.
+ *
+ * This limits the cases where we can propagate the conditional
+ * modifier. If scan_inst has a saturate modifier, then we can
+ * only propagate from inst if inst is 'scan_inst <= 0',
+ * 'scan_inst == 0', 'scan_inst != 0', or 'scan_inst > 0'. If
+ * inst is 'scan_inst == 0', the conditional modifier must be
+ * replace with LE. Likewise, if inst is 'scan_inst != 0', the
+ * conditional modifier must be replace with G.
+ *
+ * The only other cases are 'scan_inst < 0' (which is a
+ * contradiction) and 'scan_inst >= 0' (which is a tautology).
+ */
+ if (scan_inst->saturate) {
+ if (scan_inst->dst.type != BRW_REGISTER_TYPE_F)
+ break;
+
+ if (cond != BRW_CONDITIONAL_Z &&
+ cond != BRW_CONDITIONAL_NZ &&
+ cond != BRW_CONDITIONAL_LE &&
+ cond != BRW_CONDITIONAL_G)
+ break;
+
+ if (inst->opcode != BRW_OPCODE_MOV &&
+ inst->opcode != BRW_OPCODE_CMP)
+ break;
+
+ /* inst->src[1].is_zero() was tested before, but be safe
+ * against possible future changes in this code.
+ */
+ assert(inst->opcode != BRW_OPCODE_CMP || inst->src[1].is_zero());
+
+ if (cond == BRW_CONDITIONAL_Z)
+ cond = BRW_CONDITIONAL_LE;
+ else if (cond == BRW_CONDITIONAL_NZ)
+ cond = BRW_CONDITIONAL_G;
+ }
+
+ /* Otherwise, try propagating the conditional. */
if (scan_inst->can_do_cmod() &&
((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) ||
scan_inst->conditional_mod == cond)) {
scan_inst->conditional_mod = cond;
+ scan_inst->flag_subreg = inst->flag_subreg;
inst->remove(block);
progress = true;
}
break;
}
- if (scan_inst->flags_written())
+ if ((scan_inst->flags_written() & flags_written) != 0)
break;
- read_flag = read_flag || scan_inst->flags_read(devinfo);
+ read_flag = read_flag ||
+ (scan_inst->flags_read(devinfo) & flags_written) != 0;
}
}
}
if (progress)
- invalidate_live_intervals();
+ invalidate_analysis(DEPENDENCY_INSTRUCTIONS);
return progress;
}
projects / mesa.git / blobdiff