i965/fs: Factor out calculation of the block of MRFs reserved for spilling.
And as we're at it fix the calculation to allocate a larger block of registers for 32-wide dispatch. Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
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@ -723,6 +723,47 @@ fs_visitor::assign_regs(bool allow_spilling, bool spill_all)
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return true;
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}
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namespace {
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/**
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* Maximum spill block size we expect to encounter in 32B units.
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*
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* This is somewhat arbitrary and doesn't necessarily limit the maximum
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* variable size that can be spilled -- A higher value will allow a
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* variable of a given size to be spilled more efficiently with a smaller
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* number of scratch messages, but will increase the likelihood of a
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* collision between the MRFs reserved for spilling and other MRFs used by
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* the program (and possibly increase GRF register pressure on platforms
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* without hardware MRFs), what could cause register allocation to fail.
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*
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* For the moment reserve just enough space so a register of 32 bit
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* component type and natural region width can be spilled without splitting
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* into multiple (force_writemask_all) scratch messages.
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*/
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unsigned
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spill_max_size(const backend_shader *s)
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{
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/* FINISHME - On Gen7+ it should be possible to avoid this limit
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* altogether by spilling directly from the temporary GRF
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* allocated to hold the result of the instruction (and the
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* scratch write header).
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*/
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/* FINISHME - The shader's dispatch width probably belongs in
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* backend_shader (or some nonexistent fs_shader class?)
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* rather than in the visitor class.
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*/
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return static_cast<const fs_visitor *>(s)->dispatch_width / 8;
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}
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/**
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* First MRF register available for spilling.
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*/
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unsigned
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spill_base_mrf(const backend_shader *s)
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{
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return BRW_MAX_MRF(s->devinfo->gen) - spill_max_size(s) - 1;
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}
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}
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void
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fs_visitor::emit_unspill(bblock_t *block, fs_inst *inst, fs_reg dst,
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uint32_t spill_offset, int count)
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@ -753,7 +794,7 @@ fs_visitor::emit_unspill(bblock_t *block, fs_inst *inst, fs_reg dst,
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unspill_inst->regs_written = reg_size;
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if (!gen7_read) {
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unspill_inst->base_mrf = FIRST_SPILL_MRF(devinfo->gen) + 1;
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unspill_inst->base_mrf = spill_base_mrf(this);
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unspill_inst->mlen = 1; /* header contains offset */
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}
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@ -767,11 +808,8 @@ fs_visitor::emit_spill(bblock_t *block, fs_inst *inst, fs_reg src,
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uint32_t spill_offset, int count)
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{
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int reg_size = 1;
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int spill_base_mrf = FIRST_SPILL_MRF(devinfo->gen) + 1;
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if (dispatch_width == 16 && count % 2 == 0) {
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spill_base_mrf = FIRST_SPILL_MRF(devinfo->gen);
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if (dispatch_width == 16 && count % 2 == 0)
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reg_size = 2;
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}
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const fs_builder ibld = bld.annotate(inst->annotation, inst->ir)
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.group(reg_size * 8, 0)
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@ -783,7 +821,7 @@ fs_visitor::emit_spill(bblock_t *block, fs_inst *inst, fs_reg src,
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src.reg_offset += reg_size;
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spill_inst->offset = spill_offset + i * reg_size * REG_SIZE;
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spill_inst->mlen = 1 + reg_size; /* header, value */
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spill_inst->base_mrf = spill_base_mrf;
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spill_inst->base_mrf = spill_base_mrf(this);
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}
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}
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@ -869,8 +907,6 @@ fs_visitor::spill_reg(int spill_reg)
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int size = alloc.sizes[spill_reg];
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unsigned int spill_offset = last_scratch;
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assert(ALIGN(spill_offset, 16) == spill_offset); /* oword read/write req. */
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int spill_base_mrf = dispatch_width > 8 ? FIRST_SPILL_MRF(devinfo->gen) :
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FIRST_SPILL_MRF(devinfo->gen) + 1;
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/* Spills may use MRFs 13-15 in the SIMD16 case. Our texturing is done
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* using up to 11 MRFs starting from either m1 or m2, and fb writes can use
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@ -883,7 +919,7 @@ fs_visitor::spill_reg(int spill_reg)
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bool mrf_used[BRW_MAX_MRF(devinfo->gen)];
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get_used_mrfs(this, mrf_used);
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for (int i = spill_base_mrf; i < BRW_MAX_MRF(devinfo->gen); i++) {
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for (int i = spill_base_mrf(this); i < BRW_MAX_MRF(devinfo->gen); i++) {
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if (mrf_used[i]) {
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fail("Register spilling not supported with m%d used", i);
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return;
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