[Mesa-dev] [PATCH v2 043/103] i965/vec4: handle 32 and 64 bit channels in liveness analysis
Francisco Jerez
currojerez at riseup.net
Mon Dec 19 21:58:43 UTC 2016
Iago Toral Quiroga <itoral at igalia.com> writes:
> From: "Juan A. Suarez Romero" <jasuarez at igalia.com>
>
> Our current data flow analysis does not take into account that channels
> on 64-bit operands are 64-bit. This is a problem when the same register
> is accessed using both 64-bit and 32-bit channels. This is very common
> in operations where we need to access 64-bit data in 32-bit chunks,
> such as the double packing and packing operations.
>
> This patch changes the analysis by checking the bits that each source
> or destination datatype needs. Actually, rather than bits, we use
> blocks of 32bits, which is the minimum channel size.
>
> Because a vgrf can contain a dvec4 (256 bits), we reserve 8
> 32-bit blocks to map the channels.
>
> v2 (Curro):
> - Simplify code by making the var_from_reg helpers take an extra
> argument with the register component we want.
> - Fix a couple of cases where we had to update the code to the new
> way of representing live variables.
> ---
> src/mesa/drivers/dri/i965/brw_vec4.cpp | 2 +-
> src/mesa/drivers/dri/i965/brw_vec4_cse.cpp | 2 +-
> .../dri/i965/brw_vec4_dead_code_eliminate.cpp | 25 +++++++++--------
> .../drivers/dri/i965/brw_vec4_live_variables.cpp | 32 +++++++++++-----------
> .../drivers/dri/i965/brw_vec4_live_variables.h | 15 ++++++----
> 5 files changed, 42 insertions(+), 34 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
> index 3191eab..34cab04 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
> @@ -1140,7 +1140,7 @@ vec4_visitor::opt_register_coalesce()
> /* Can't coalesce this GRF if someone else was going to
> * read it later.
> */
> - if (var_range_end(var_from_reg(alloc, dst_reg(inst->src[0])), 4) > ip)
> + if (var_range_end(var_from_reg(alloc, dst_reg(inst->src[0])), 8) > ip)
> continue;
>
> /* We need to check interference with the final destination between this
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp b/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
> index 1b91db9..bef897a 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
> @@ -246,7 +246,7 @@ vec4_visitor::opt_cse_local(bblock_t *block)
> * more -- a sure sign they'll fail operands_match().
> */
> if (src->file == VGRF) {
> - if (var_range_end(var_from_reg(alloc, dst_reg(*src)), 4) < ip) {
> + if (var_range_end(var_from_reg(alloc, dst_reg(*src)), 8) < ip) {
> entry->remove();
> ralloc_free(entry);
> break;
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp b/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
> index 950c6c8..6a80810 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
> @@ -57,12 +57,13 @@ vec4_visitor::dead_code_eliminate()
> if ((inst->dst.file == VGRF && !inst->has_side_effects()) ||
> (inst->dst.is_null() && inst->writes_flag())){
> bool result_live[4] = { false };
> -
> if (inst->dst.file == VGRF) {
> - for (unsigned i = 0; i < regs_written(inst); i++) {
> - for (int c = 0; c < 4; c++)
> - result_live[c] |= BITSET_TEST(
> - live, var_from_reg(alloc, offset(inst->dst, i), c));
> + for (unsigned i = 0; i < 2 * regs_written(inst); i++) {
One of the issues we discussed in the past about this approach is that
it would overestimate the number of register OWORDs accessed by
instructions with size_written < REG_SIZE (or size_read(i) < REG_SIZE),
which will be emitted by the SIMD lowering pass. Now that the amount of
data read and written by instructions is represented in byte units you
can avoid this problem by using DIV_ROUND_UP(inst->size_written, 16)
instead of 2 * regs_written(inst) above.
> + for (int c = 0; c < 4; c++) {
> + const unsigned v =
> + var_from_reg(alloc, inst->dst, c, i);
> + result_live[c] |= BITSET_TEST(live, v);
> + }
> }
> } else {
> for (unsigned c = 0; c < 4; c++)
> @@ -111,11 +112,12 @@ vec4_visitor::dead_code_eliminate()
>
> if (inst->dst.file == VGRF && !inst->predicate &&
> !inst->is_align1_partial_write()) {
> - for (unsigned i = 0; i < regs_written(inst); i++) {
> + for (unsigned i = 0; i < 2 * regs_written(inst); i++) {
Same rounding issue as above.
> for (int c = 0; c < 4; c++) {
> if (inst->dst.writemask & (1 << c)) {
> - BITSET_CLEAR(live, var_from_reg(alloc,
> - offset(inst->dst, i), c));
> + const unsigned v =
> + var_from_reg(alloc, inst->dst, c, i);
> + BITSET_CLEAR(live, v);
> }
> }
> }
> @@ -133,10 +135,11 @@ vec4_visitor::dead_code_eliminate()
>
> for (int i = 0; i < 3; i++) {
> if (inst->src[i].file == VGRF) {
> - for (unsigned j = 0; j < regs_read(inst, i); j++) {
> + for (unsigned j = 0; j < 2 * regs_read(inst, i); j++) {
Same rounding issue as above.
> for (int c = 0; c < 4; c++) {
> - BITSET_SET(live, var_from_reg(alloc,
> - offset(inst->src[i], j), c));
> + const unsigned v =
> + var_from_reg(alloc, inst->src[i], c, j);
> + BITSET_SET(live, v);
> }
> }
> }
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4_live_variables.cpp b/src/mesa/drivers/dri/i965/brw_vec4_live_variables.cpp
> index 20344ed..4827798 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4_live_variables.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_vec4_live_variables.cpp
> @@ -76,10 +76,10 @@ vec4_live_variables::setup_def_use()
> /* Set use[] for this instruction */
> for (unsigned int i = 0; i < 3; i++) {
> if (inst->src[i].file == VGRF) {
> - for (unsigned j = 0; j < regs_read(inst, i); j++) {
> + for (unsigned j = 0; j < 2 * regs_read(inst, i); j++) {
Same rounding issue as above.
> for (int c = 0; c < 4; c++) {
> const unsigned v =
> - var_from_reg(alloc, offset(inst->src[i], j), c);
> + var_from_reg(alloc, inst->src[i], c, j);
> if (!BITSET_TEST(bd->def, v))
> BITSET_SET(bd->use, v);
> }
> @@ -99,11 +99,11 @@ vec4_live_variables::setup_def_use()
> */
> if (inst->dst.file == VGRF &&
> (!inst->predicate || inst->opcode == BRW_OPCODE_SEL)) {
> - for (unsigned i = 0; i < regs_written(inst); i++) {
> + for (unsigned i = 0; i < 2 * regs_written(inst); i++) {
Same rounding issue as above.
> for (int c = 0; c < 4; c++) {
> if (inst->dst.writemask & (1 << c)) {
> const unsigned v =
> - var_from_reg(alloc, offset(inst->dst, i), c);
> + var_from_reg(alloc, inst->dst, c, i);
> if (!BITSET_TEST(bd->use, v))
> BITSET_SET(bd->def, v);
> }
> @@ -188,7 +188,7 @@ vec4_live_variables::vec4_live_variables(const simple_allocator &alloc,
> {
> mem_ctx = ralloc_context(NULL);
>
> - num_vars = alloc.total_size * 4;
> + num_vars = alloc.total_size * 8;
> block_data = rzalloc_array(mem_ctx, struct block_data, cfg->num_blocks);
>
> bitset_words = BITSET_WORDS(num_vars);
> @@ -238,14 +238,14 @@ vec4_visitor::calculate_live_intervals()
> if (this->live_intervals)
> return;
>
> - int *start = ralloc_array(mem_ctx, int, this->alloc.total_size * 4);
> - int *end = ralloc_array(mem_ctx, int, this->alloc.total_size * 4);
> + int *start = ralloc_array(mem_ctx, int, this->alloc.total_size * 8);
> + int *end = ralloc_array(mem_ctx, int, this->alloc.total_size * 8);
> ralloc_free(this->virtual_grf_start);
> ralloc_free(this->virtual_grf_end);
> this->virtual_grf_start = start;
> this->virtual_grf_end = end;
>
> - for (unsigned i = 0; i < this->alloc.total_size * 4; i++) {
> + for (unsigned i = 0; i < this->alloc.total_size * 8; i++) {
> start[i] = MAX_INSTRUCTION;
> end[i] = -1;
> }
> @@ -257,10 +257,10 @@ vec4_visitor::calculate_live_intervals()
> foreach_block_and_inst(block, vec4_instruction, inst, cfg) {
> for (unsigned int i = 0; i < 3; i++) {
> if (inst->src[i].file == VGRF) {
> - for (unsigned j = 0; j < regs_read(inst, i); j++) {
> + for (unsigned j = 0; j < 2 * regs_read(inst, i); j++) {
Same rounding issue as above.
> for (int c = 0; c < 4; c++) {
> const unsigned v =
> - var_from_reg(alloc, offset(inst->src[i], j), c);
> + var_from_reg(alloc, inst->src[i], c, j);
> start[v] = MIN2(start[v], ip);
> end[v] = ip;
> }
> @@ -269,11 +269,11 @@ vec4_visitor::calculate_live_intervals()
> }
>
> if (inst->dst.file == VGRF) {
> - for (unsigned i = 0; i < regs_written(inst); i++) {
> + for (unsigned i = 0; i < 2 * regs_written(inst); i++) {
Same rounding issue as above.
> for (int c = 0; c < 4; c++) {
> if (inst->dst.writemask & (1 << c)) {
> const unsigned v =
> - var_from_reg(alloc, offset(inst->dst, i), c);
> + var_from_reg(alloc, inst->dst, c, i);
> start[v] = MIN2(start[v], ip);
> end[v] = ip;
> }
> @@ -340,8 +340,8 @@ vec4_visitor::var_range_end(unsigned v, unsigned n) const
> bool
> vec4_visitor::virtual_grf_interferes(int a, int b)
> {
> - return !((var_range_end(4 * alloc.offsets[a], 4 * alloc.sizes[a]) <=
> - var_range_start(4 * alloc.offsets[b], 4 * alloc.sizes[b])) ||
> - (var_range_end(4 * alloc.offsets[b], 4 * alloc.sizes[b]) <=
> - var_range_start(4 * alloc.offsets[a], 4 * alloc.sizes[a])));
> + return !((var_range_end(8 * alloc.offsets[a], 8 * alloc.sizes[a]) <=
> + var_range_start(8 * alloc.offsets[b], 8 * alloc.sizes[b])) ||
> + (var_range_end(8 * alloc.offsets[b], 8 * alloc.sizes[b]) <=
> + var_range_start(8 * alloc.offsets[a], 8 * alloc.sizes[a])));
> }
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4_live_variables.h b/src/mesa/drivers/dri/i965/brw_vec4_live_variables.h
> index 2fbcaa1..26a074f 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4_live_variables.h
> +++ b/src/mesa/drivers/dri/i965/brw_vec4_live_variables.h
> @@ -78,23 +78,28 @@ protected:
> void *mem_ctx;
> };
>
> +/* Returns the variable index for the k-th dword of the c-th component of
> + * register reg */
Non-standard comment formatting.
> inline unsigned
> var_from_reg(const simple_allocator &alloc, const src_reg ®,
> - unsigned c = 0)
> + unsigned c = 0, unsigned k = 0)
Odd indentation.
> {
> assert(reg.file == VGRF && reg.nr < alloc.count &&
> reg.offset / REG_SIZE < alloc.sizes[reg.nr] && c < 4);
You could simplify this to "assert(reg.file == VGRF && reg.nr <
alloc.count && c < 4)", and move the rest of the assertion after the
calculation so you can make sure that the result (including terms
dependent on k) is less than "8 * alloc.sizes[reg.nr]".
> - return (4 * (alloc.offsets[reg.nr] + reg.offset / REG_SIZE) +
> - BRW_GET_SWZ(reg.swizzle, c));
> + const unsigned csize = DIV_ROUND_UP(type_sz(reg.type), 4);
> + return 8 * (alloc.offsets[reg.nr] + reg.offset / REG_SIZE) +
> + (BRW_GET_SWZ(reg.swizzle, c) + k / csize * 4) * csize + k % csize;
> }
>
> inline unsigned
> var_from_reg(const simple_allocator &alloc, const dst_reg ®,
> - unsigned c = 0)
> + unsigned c = 0, unsigned k = 0)
Odd indentation.
> {
> assert(reg.file == VGRF && reg.nr < alloc.count &&
> reg.offset / REG_SIZE < alloc.sizes[reg.nr] && c < 4);
Same suggestion as for your last assert.
> - return 4 * (alloc.offsets[reg.nr] + reg.offset / REG_SIZE) + c;
> + const unsigned csize = DIV_ROUND_UP(type_sz(reg.type), 4);
> + return 8 * (alloc.offsets[reg.nr] + reg.offset / REG_SIZE) +
> + (c + k / csize * 4) * csize + k % csize;
> }
>
> } /* namespace brw */
> --
> 2.7.4
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