src/panfrost/midgard/mir.c - third_party/mesa - Git at Google

 /*
  * Copyright (C) 2019 Alyssa Rosenzweig <alyssa@rosenzweig.io>
  * Copyright (C) 2019-2020 Collabora, Ltd.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  * and/or sell copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice (including the next
  * paragraph) shall be included in all copies or substantial portions of the
  * Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */

 #include "compiler.h"
 #include "midgard_ops.h"

 void mir_rewrite_index_src_single(midgard_instruction *ins, unsigned old, unsigned new)
 {
         mir_foreach_src(ins, i) {
                 if (ins->src[i] == old)
                         ins->src[i] = new;
         }
 }

 void mir_rewrite_index_dst_single(midgard_instruction *ins, unsigned old, unsigned new)
 {
         if (ins->dest == old)
                 ins->dest = new;
 }

 static void
 mir_rewrite_index_src_single_swizzle(midgard_instruction *ins, unsigned old, unsigned new, unsigned *swizzle)
 {
         for (unsigned i = 0; i < ARRAY_SIZE(ins->src); ++i) {
                 if (ins->src[i] != old) continue;

                 ins->src[i] = new;
                 mir_compose_swizzle(ins->swizzle[i], swizzle, ins->swizzle[i]);
         }
 }

 void
 mir_rewrite_index_src(compiler_context *ctx, unsigned old, unsigned new)
 {
         mir_foreach_instr_global(ctx, ins) {
                 mir_rewrite_index_src_single(ins, old, new);
         }
 }

 void
 mir_rewrite_index_src_swizzle(compiler_context *ctx, unsigned old, unsigned new, unsigned *swizzle)
 {
         mir_foreach_instr_global(ctx, ins) {
                 mir_rewrite_index_src_single_swizzle(ins, old, new, swizzle);
         }
 }

 void
 mir_rewrite_index_dst(compiler_context *ctx, unsigned old, unsigned new)
 {
         mir_foreach_instr_global(ctx, ins) {
                 mir_rewrite_index_dst_single(ins, old, new);
         }

         /* Implicitly written before the shader */
         if (ctx->blend_input == old)
                 ctx->blend_input = new;

         if (ctx->blend_src1 == old)
                 ctx->blend_src1 = new;
 }

 void
 mir_rewrite_index(compiler_context *ctx, unsigned old, unsigned new)
 {
         mir_rewrite_index_src(ctx, old, new);
         mir_rewrite_index_dst(ctx, old, new);
 }

 unsigned
 mir_use_count(compiler_context *ctx, unsigned value)
 {
         unsigned used_count = 0;

         mir_foreach_instr_global(ctx, ins) {
                 if (mir_has_arg(ins, value))
                         ++used_count;
         }

         if (ctx->blend_input == value)
                 ++used_count;

         if (ctx->blend_src1 == value)
                 ++used_count;

         return used_count;
 }

 /* Checks if a value is used only once (or totally dead), which is an important
  * heuristic to figure out if certain optimizations are Worth It (TM) */

 bool
 mir_single_use(compiler_context *ctx, unsigned value)
 {
         /* We can replicate constants in places so who cares */
         if (value == SSA_FIXED_REGISTER(REGISTER_CONSTANT))
                 return true;

         return mir_use_count(ctx, value) <= 1;
 }

 bool
 mir_nontrivial_mod(midgard_instruction *ins, unsigned i, bool check_swizzle)
 {
         bool is_int = midgard_is_integer_op(ins->op);

         if (is_int) {
                 if (ins->src_shift[i]) return true;
         } else {
                 if (ins->src_neg[i]) return true;
                 if (ins->src_abs[i]) return true;
         }

         if (ins->dest_type != ins->src_types[i]) return true;

         if (check_swizzle) {
                 for (unsigned c = 0; c < 16; ++c) {
                         if (!(ins->mask & (1 << c))) continue;
                         if (ins->swizzle[i][c] != c) return true;
                 }
         }

         return false;
 }

 bool
 mir_nontrivial_outmod(midgard_instruction *ins)
 {
         bool is_int = midgard_is_integer_op(ins->op);
         unsigned mod = ins->outmod;

         if (ins->dest_type != ins->src_types[1])
                 return true;

         if (is_int)
                 return mod != midgard_outmod_keeplo;
         else
                 return mod != midgard_outmod_none;
 }

 /* 128 / sz = exp2(log2(128 / sz))
  *          = exp2(log2(128) - log2(sz))
  *          = exp2(7 - log2(sz))
  *          = 1 << (7 - log2(sz))
  */

 static unsigned
 mir_components_for_bits(unsigned bits)
 {
         return 1 << (7 - util_logbase2(bits));
 }

 unsigned
 mir_components_for_type(nir_alu_type T)
 {
         unsigned sz = nir_alu_type_get_type_size(T);
         return mir_components_for_bits(sz);
 }

 uint16_t
 mir_from_bytemask(uint16_t bytemask, unsigned bits)
 {
         unsigned value = 0;
         unsigned count = bits / 8;

         for (unsigned c = 0, d = 0; c < 16; c += count, ++d) {
                 bool a = (bytemask & (1 << c)) != 0;

                 for (unsigned q = c; q < count; ++q)
                         assert(((bytemask & (1 << q)) != 0) == a);

                 value |= (a << d);
         }

         return value;
 }

 /* Rounds up a bytemask to fill a given component count. Iterate each
  * component, and check if any bytes in the component are masked on */

 uint16_t
 mir_round_bytemask_up(uint16_t mask, unsigned bits)
 {
         unsigned bytes = bits / 8;
         unsigned maxmask = mask_of(bytes);
         unsigned channels = mir_components_for_bits(bits);

         for (unsigned c = 0; c < channels; ++c) {
                 unsigned submask = maxmask << (c * bytes);

                 if (mask & submask)
                         mask |= submask;
         }

         return mask;
 }

 /* Grabs the per-byte mask of an instruction (as opposed to per-component) */

 uint16_t
 mir_bytemask(midgard_instruction *ins)
 {
         unsigned type_size = nir_alu_type_get_type_size(ins->dest_type);
         return pan_to_bytemask(type_size, ins->mask);
 }

 void
 mir_set_bytemask(midgard_instruction *ins, uint16_t bytemask)
 {
         unsigned type_size = nir_alu_type_get_type_size(ins->dest_type);
         ins->mask = mir_from_bytemask(bytemask, type_size);
 }

 /*
  * Checks if we should use an upper destination override, rather than the lower
  * one in the IR. If yes, returns the bytes to shift by. If no, returns zero
  * for a lower override and negative for no override.
  */
 signed
 mir_upper_override(midgard_instruction *ins, unsigned inst_size)
 {
         unsigned type_size = nir_alu_type_get_type_size(ins->dest_type);

         /* If the sizes are the same, there's nothing to override */
         if (type_size == inst_size)
                 return -1;

         /* There are 16 bytes per vector, so there are (16/bytes)
          * components per vector. So the magic half is half of
          * (16/bytes), which simplifies to 8/bytes = 8 / (bits / 8) = 64 / bits
          * */

         unsigned threshold = mir_components_for_bits(type_size) >> 1;

         /* How many components did we shift over? */
         unsigned zeroes = __builtin_ctz(ins->mask);

         /* Did we hit the threshold? */
         return (zeroes >= threshold) ? threshold : 0;
 }

 /* Creates a mask of the components of a node read by an instruction, by
  * analyzing the swizzle with respect to the instruction's mask. E.g.:
  *
  *  fadd r0.xz, r1.yyyy, r2.zwyx
  *
  * will return a mask of Z/Y for r2
  */

 static uint16_t
 mir_bytemask_of_read_components_single(unsigned *swizzle, unsigned inmask, unsigned bits)
 {
         unsigned cmask = 0;

         for (unsigned c = 0; c < MIR_VEC_COMPONENTS; ++c) {
                 if (!(inmask & (1 << c))) continue;
                 cmask |= (1 << swizzle[c]);
         }

         return pan_to_bytemask(bits, cmask);
 }

 uint16_t
 mir_bytemask_of_read_components_index(midgard_instruction *ins, unsigned i)
 {
         /* Conditional branches read one 32-bit component = 4 bytes (TODO: multi branch??) */
         if (ins->compact_branch && ins->branch.conditional && (i == 0))
                 return 0xF;

         /* ALU ops act componentwise so we need to pay attention to
          * their mask. Texture/ldst does not so we don't clamp source
          * readmasks based on the writemask */
         unsigned qmask = ~0;

         /* Handle dot products and things */
         if (ins->type == TAG_ALU_4 && !ins->compact_branch) {
                 unsigned props = alu_opcode_props[ins->op].props;

                 unsigned channel_override = GET_CHANNEL_COUNT(props);

                 if (channel_override)
                         qmask = mask_of(channel_override);
                 else
                         qmask = ins->mask;
         }

         return mir_bytemask_of_read_components_single(ins->swizzle[i], qmask,
                 nir_alu_type_get_type_size(ins->src_types[i]));
 }

 uint16_t
 mir_bytemask_of_read_components(midgard_instruction *ins, unsigned node)
 {
         uint16_t mask = 0;

         if (node == ~0)
                 return 0;

         mir_foreach_src(ins, i) {
                 if (ins->src[i] != node) continue;
                 mask |= mir_bytemask_of_read_components_index(ins, i);
         }

         return mask;
 }

 /* Register allocation occurs after instruction scheduling, which is fine until
  * we start needing to spill registers and therefore insert instructions into
  * an already-scheduled program. We don't have to be terribly efficient about
  * this, since spilling is already slow. So just semantically we need to insert
  * the instruction into a new bundle before/after the bundle of the instruction
  * in question */

 static midgard_bundle
 mir_bundle_for_op(compiler_context *ctx, midgard_instruction ins)
 {
         midgard_instruction *u = mir_upload_ins(ctx, ins);

         midgard_bundle bundle = {
                 .tag = ins.type,
                 .instruction_count = 1,
                 .instructions = { u },
         };

         if (bundle.tag == TAG_ALU_4) {
                 assert(OP_IS_MOVE(u->op));
                 u->unit = UNIT_VMUL;

                 size_t bytes_emitted = sizeof(uint32_t) + sizeof(midgard_reg_info) + sizeof(midgard_vector_alu);
                 bundle.padding = ~(bytes_emitted - 1) & 0xF;
                 bundle.control = ins.type | u->unit;
         }

         return bundle;
 }

 static unsigned
 mir_bundle_idx_for_ins(midgard_instruction *tag, midgard_block *block)
 {
         midgard_bundle *bundles =
                 (midgard_bundle *) block->bundles.data;

         size_t count = (block->bundles.size / sizeof(midgard_bundle));

         for (unsigned i = 0; i < count; ++i) {
                 for (unsigned j = 0; j < bundles[i].instruction_count; ++j) {
                         if (bundles[i].instructions[j] == tag)
                                 return i;
                 }
         }

         mir_print_instruction(tag);
         unreachable("Instruction not scheduled in block");
 }

 midgard_instruction *
 mir_insert_instruction_before_scheduled(
         compiler_context *ctx,
         midgard_block *block,
         midgard_instruction *tag,
         midgard_instruction ins)
 {
         unsigned before = mir_bundle_idx_for_ins(tag, block);
         size_t count = util_dynarray_num_elements(&block->bundles, midgard_bundle);
         UNUSED void *unused = util_dynarray_grow(&block->bundles, midgard_bundle, 1);

         midgard_bundle *bundles = (midgard_bundle *) block->bundles.data;
         memmove(bundles + before + 1, bundles + before, (count - before) * sizeof(midgard_bundle));
         midgard_bundle *before_bundle = bundles + before + 1;

         midgard_bundle new = mir_bundle_for_op(ctx, ins);
         memcpy(bundles + before, &new, sizeof(new));

         list_addtail(&new.instructions[0]->link, &before_bundle->instructions[0]->link);
         block->quadword_count += midgard_tag_props[new.tag].size;

         return new.instructions[0];
 }

 midgard_instruction *
 mir_insert_instruction_after_scheduled(
         compiler_context *ctx,
         midgard_block *block,
         midgard_instruction *tag,
         midgard_instruction ins)
 {
         /* We need to grow the bundles array to add our new bundle */
         size_t count = util_dynarray_num_elements(&block->bundles, midgard_bundle);
         UNUSED void *unused = util_dynarray_grow(&block->bundles, midgard_bundle, 1);

         /* Find the bundle that we want to insert after */
         unsigned after = mir_bundle_idx_for_ins(tag, block);

         /* All the bundles after that one, we move ahead by one */
         midgard_bundle *bundles = (midgard_bundle *) block->bundles.data;
         memmove(bundles + after + 2, bundles + after + 1, (count - after - 1) * sizeof(midgard_bundle));
         midgard_bundle *after_bundle = bundles + after;

         midgard_bundle new = mir_bundle_for_op(ctx, ins);
         memcpy(bundles + after + 1, &new, sizeof(new));
         list_add(&new.instructions[0]->link, &after_bundle->instructions[after_bundle->instruction_count - 1]->link);
         block->quadword_count += midgard_tag_props[new.tag].size;

         return new.instructions[0];
 }

 /* Flip the first-two arguments of a (binary) op. Currently ALU
  * only, no known uses for ldst/tex */

 void
 mir_flip(midgard_instruction *ins)
 {
         unsigned temp = ins->src[0];
         ins->src[0] = ins->src[1];
         ins->src[1] = temp;

         assert(ins->type == TAG_ALU_4);

         temp = ins->src_types[0];
         ins->src_types[0] = ins->src_types[1];
         ins->src_types[1] = temp;

         temp = ins->src_abs[0];
         ins->src_abs[0] = ins->src_abs[1];
         ins->src_abs[1] = temp;

         temp = ins->src_neg[0];
         ins->src_neg[0] = ins->src_neg[1];
         ins->src_neg[1] = temp;

         temp = ins->src_invert[0];
         ins->src_invert[0] = ins->src_invert[1];
         ins->src_invert[1] = temp;

         unsigned temp_swizzle[16];
         memcpy(temp_swizzle, ins->swizzle[0], sizeof(ins->swizzle[0]));
         memcpy(ins->swizzle[0], ins->swizzle[1], sizeof(ins->swizzle[0]));
         memcpy(ins->swizzle[1], temp_swizzle, sizeof(ins->swizzle[0]));
 }

 /* Before squashing, calculate ctx->temp_count just by observing the MIR */

 void
 mir_compute_temp_count(compiler_context *ctx)
 {
         if (ctx->temp_count)
                 return;

         unsigned max_dest = 0;

         mir_foreach_instr_global(ctx, ins) {
                 if (ins->dest < SSA_FIXED_MINIMUM)
                         max_dest = MAX2(max_dest, ins->dest + 1);
         }

         ctx->temp_count = max_dest;
 }
	/*
	* Copyright (C) 2019 Alyssa Rosenzweig <alyssa@rosenzweig.io>
	* Copyright (C) 2019-2020 Collabora, Ltd.
	*
	* Permission is hereby granted, free of charge, to any person obtaining a
	* copy of this software and associated documentation files (the "Software"),
	* to deal in the Software without restriction, including without limitation
	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
	* and/or sell copies of the Software, and to permit persons to whom the
	* Software is furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice (including the next
	* paragraph) shall be included in all copies or substantial portions of the
	* Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	* SOFTWARE.
	*/

	#include "compiler.h"
	#include "midgard_ops.h"

	void mir_rewrite_index_src_single(midgard_instruction *ins, unsigned old, unsigned new)
	{
	mir_foreach_src(ins, i) {
	if (ins->src[i] == old)
	ins->src[i] = new;
	}
	}

	void mir_rewrite_index_dst_single(midgard_instruction *ins, unsigned old, unsigned new)
	{
	if (ins->dest == old)
	ins->dest = new;
	}

	static void
	mir_rewrite_index_src_single_swizzle(midgard_instruction ins, unsigned old, unsigned new, unsigned swizzle)
	{
	for (unsigned i = 0; i < ARRAY_SIZE(ins->src); ++i) {
	if (ins->src[i] != old) continue;

	ins->src[i] = new;
	mir_compose_swizzle(ins->swizzle[i], swizzle, ins->swizzle[i]);
	}
	}

	void
	mir_rewrite_index_src(compiler_context *ctx, unsigned old, unsigned new)
	{
	mir_foreach_instr_global(ctx, ins) {
	mir_rewrite_index_src_single(ins, old, new);
	}
	}

	void
	mir_rewrite_index_src_swizzle(compiler_context ctx, unsigned old, unsigned new, unsigned swizzle)
	{
	mir_foreach_instr_global(ctx, ins) {
	mir_rewrite_index_src_single_swizzle(ins, old, new, swizzle);
	}
	}

	void
	mir_rewrite_index_dst(compiler_context *ctx, unsigned old, unsigned new)
	{
	mir_foreach_instr_global(ctx, ins) {
	mir_rewrite_index_dst_single(ins, old, new);
	}

	/* Implicitly written before the shader */
	if (ctx->blend_input == old)
	ctx->blend_input = new;

	if (ctx->blend_src1 == old)
	ctx->blend_src1 = new;
	}

	void
	mir_rewrite_index(compiler_context *ctx, unsigned old, unsigned new)
	{
	mir_rewrite_index_src(ctx, old, new);
	mir_rewrite_index_dst(ctx, old, new);
	}

	unsigned
	mir_use_count(compiler_context *ctx, unsigned value)
	{
	unsigned used_count = 0;

	mir_foreach_instr_global(ctx, ins) {
	if (mir_has_arg(ins, value))
	++used_count;
	}

	if (ctx->blend_input == value)
	++used_count;

	if (ctx->blend_src1 == value)
	++used_count;

	return used_count;
	}

	/* Checks if a value is used only once (or totally dead), which is an important
	* heuristic to figure out if certain optimizations are Worth It (TM) */

	bool
	mir_single_use(compiler_context *ctx, unsigned value)
	{
	/* We can replicate constants in places so who cares */
	if (value == SSA_FIXED_REGISTER(REGISTER_CONSTANT))
	return true;

	return mir_use_count(ctx, value) <= 1;
	}

	bool
	mir_nontrivial_mod(midgard_instruction *ins, unsigned i, bool check_swizzle)
	{
	bool is_int = midgard_is_integer_op(ins->op);

	if (is_int) {
	if (ins->src_shift[i]) return true;
	} else {
	if (ins->src_neg[i]) return true;
	if (ins->src_abs[i]) return true;
	}

	if (ins->dest_type != ins->src_types[i]) return true;

	if (check_swizzle) {
	for (unsigned c = 0; c < 16; ++c) {
	if (!(ins->mask & (1 << c))) continue;
	if (ins->swizzle[i][c] != c) return true;
	}
	}

	return false;
	}

	bool
	mir_nontrivial_outmod(midgard_instruction *ins)
	{
	bool is_int = midgard_is_integer_op(ins->op);
	unsigned mod = ins->outmod;

	if (ins->dest_type != ins->src_types[1])
	return true;

	if (is_int)
	return mod != midgard_outmod_keeplo;
	else
	return mod != midgard_outmod_none;
	}

	/* 128 / sz = exp2(log2(128 / sz))
	* = exp2(log2(128) - log2(sz))
	* = exp2(7 - log2(sz))
	* = 1 << (7 - log2(sz))
	*/

	static unsigned
	mir_components_for_bits(unsigned bits)
	{
	return 1 << (7 - util_logbase2(bits));
	}

	unsigned
	mir_components_for_type(nir_alu_type T)
	{
	unsigned sz = nir_alu_type_get_type_size(T);
	return mir_components_for_bits(sz);
	}

	uint16_t
	mir_from_bytemask(uint16_t bytemask, unsigned bits)
	{
	unsigned value = 0;
	unsigned count = bits / 8;

	for (unsigned c = 0, d = 0; c < 16; c += count, ++d) {
	bool a = (bytemask & (1 << c)) != 0;

	for (unsigned q = c; q < count; ++q)
	assert(((bytemask & (1 << q)) != 0) == a);

	value \|= (a << d);
	}

	return value;
	}

	/* Rounds up a bytemask to fill a given component count. Iterate each
	* component, and check if any bytes in the component are masked on */

	uint16_t
	mir_round_bytemask_up(uint16_t mask, unsigned bits)
	{
	unsigned bytes = bits / 8;
	unsigned maxmask = mask_of(bytes);
	unsigned channels = mir_components_for_bits(bits);

	for (unsigned c = 0; c < channels; ++c) {
	unsigned submask = maxmask << (c * bytes);

	if (mask & submask)
	mask \|= submask;
	}

	return mask;
	}

	/* Grabs the per-byte mask of an instruction (as opposed to per-component) */

	uint16_t
	mir_bytemask(midgard_instruction *ins)
	{
	unsigned type_size = nir_alu_type_get_type_size(ins->dest_type);
	return pan_to_bytemask(type_size, ins->mask);
	}

	void
	mir_set_bytemask(midgard_instruction *ins, uint16_t bytemask)
	{
	unsigned type_size = nir_alu_type_get_type_size(ins->dest_type);
	ins->mask = mir_from_bytemask(bytemask, type_size);
	}

	/*
	* Checks if we should use an upper destination override, rather than the lower
	* one in the IR. If yes, returns the bytes to shift by. If no, returns zero
	* for a lower override and negative for no override.
	*/
	signed
	mir_upper_override(midgard_instruction *ins, unsigned inst_size)
	{
	unsigned type_size = nir_alu_type_get_type_size(ins->dest_type);

	/* If the sizes are the same, there's nothing to override */
	if (type_size == inst_size)
	return -1;

	/* There are 16 bytes per vector, so there are (16/bytes)
	* components per vector. So the magic half is half of
	* (16/bytes), which simplifies to 8/bytes = 8 / (bits / 8) = 64 / bits
	* */

	unsigned threshold = mir_components_for_bits(type_size) >> 1;

	/* How many components did we shift over? */
	unsigned zeroes = __builtin_ctz(ins->mask);

	/* Did we hit the threshold? */
	return (zeroes >= threshold) ? threshold : 0;
	}

	/* Creates a mask of the components of a node read by an instruction, by
	* analyzing the swizzle with respect to the instruction's mask. E.g.:
	*
	* fadd r0.xz, r1.yyyy, r2.zwyx
	*
	* will return a mask of Z/Y for r2
	*/

	static uint16_t
	mir_bytemask_of_read_components_single(unsigned *swizzle, unsigned inmask, unsigned bits)
	{
	unsigned cmask = 0;

	for (unsigned c = 0; c < MIR_VEC_COMPONENTS; ++c) {
	if (!(inmask & (1 << c))) continue;
	cmask \|= (1 << swizzle[c]);
	}

	return pan_to_bytemask(bits, cmask);
	}

	uint16_t
	mir_bytemask_of_read_components_index(midgard_instruction *ins, unsigned i)
	{
	/* Conditional branches read one 32-bit component = 4 bytes (TODO: multi branch??) */
	if (ins->compact_branch && ins->branch.conditional && (i == 0))
	return 0xF;

	/* ALU ops act componentwise so we need to pay attention to
	* their mask. Texture/ldst does not so we don't clamp source
	* readmasks based on the writemask */
	unsigned qmask = ~0;

	/* Handle dot products and things */
	if (ins->type == TAG_ALU_4 && !ins->compact_branch) {
	unsigned props = alu_opcode_props[ins->op].props;

	unsigned channel_override = GET_CHANNEL_COUNT(props);

	if (channel_override)
	qmask = mask_of(channel_override);
	else
	qmask = ins->mask;
	}

	return mir_bytemask_of_read_components_single(ins->swizzle[i], qmask,
	nir_alu_type_get_type_size(ins->src_types[i]));
	}

	uint16_t
	mir_bytemask_of_read_components(midgard_instruction *ins, unsigned node)
	{
	uint16_t mask = 0;

	if (node == ~0)
	return 0;

	mir_foreach_src(ins, i) {
	if (ins->src[i] != node) continue;
	mask \|= mir_bytemask_of_read_components_index(ins, i);
	}

	return mask;
	}

	/* Register allocation occurs after instruction scheduling, which is fine until
	* we start needing to spill registers and therefore insert instructions into
	* an already-scheduled program. We don't have to be terribly efficient about
	* this, since spilling is already slow. So just semantically we need to insert
	* the instruction into a new bundle before/after the bundle of the instruction
	* in question */

	static midgard_bundle
	mir_bundle_for_op(compiler_context *ctx, midgard_instruction ins)
	{
	midgard_instruction *u = mir_upload_ins(ctx, ins);

	midgard_bundle bundle = {
	.tag = ins.type,
	.instruction_count = 1,
	.instructions = { u },
	};

	if (bundle.tag == TAG_ALU_4) {
	assert(OP_IS_MOVE(u->op));
	u->unit = UNIT_VMUL;

	size_t bytes_emitted = sizeof(uint32_t) + sizeof(midgard_reg_info) + sizeof(midgard_vector_alu);
	bundle.padding = ~(bytes_emitted - 1) & 0xF;
	bundle.control = ins.type \| u->unit;
	}

	return bundle;
	}

	static unsigned
	mir_bundle_idx_for_ins(midgard_instruction tag, midgard_block block)
	{
	midgard_bundle *bundles =
	(midgard_bundle *) block->bundles.data;

	size_t count = (block->bundles.size / sizeof(midgard_bundle));

	for (unsigned i = 0; i < count; ++i) {
	for (unsigned j = 0; j < bundles[i].instruction_count; ++j) {
	if (bundles[i].instructions[j] == tag)
	return i;
	}
	}

	mir_print_instruction(tag);
	unreachable("Instruction not scheduled in block");
	}

	midgard_instruction *
	mir_insert_instruction_before_scheduled(
	compiler_context *ctx,
	midgard_block *block,
	midgard_instruction *tag,
	midgard_instruction ins)
	{
	unsigned before = mir_bundle_idx_for_ins(tag, block);
	size_t count = util_dynarray_num_elements(&block->bundles, midgard_bundle);
	UNUSED void *unused = util_dynarray_grow(&block->bundles, midgard_bundle, 1);

	midgard_bundle bundles = (midgard_bundle ) block->bundles.data;
	memmove(bundles + before + 1, bundles + before, (count - before) * sizeof(midgard_bundle));
	midgard_bundle *before_bundle = bundles + before + 1;

	midgard_bundle new = mir_bundle_for_op(ctx, ins);
	memcpy(bundles + before, &new, sizeof(new));

	list_addtail(&new.instructions[0]->link, &before_bundle->instructions[0]->link);
	block->quadword_count += midgard_tag_props[new.tag].size;

	return new.instructions[0];
	}

	midgard_instruction *
	mir_insert_instruction_after_scheduled(
	compiler_context *ctx,
	midgard_block *block,
	midgard_instruction *tag,
	midgard_instruction ins)
	{
	/* We need to grow the bundles array to add our new bundle */
	size_t count = util_dynarray_num_elements(&block->bundles, midgard_bundle);
	UNUSED void *unused = util_dynarray_grow(&block->bundles, midgard_bundle, 1);

	/* Find the bundle that we want to insert after */
	unsigned after = mir_bundle_idx_for_ins(tag, block);

	/* All the bundles after that one, we move ahead by one */
	midgard_bundle bundles = (midgard_bundle ) block->bundles.data;
	memmove(bundles + after + 2, bundles + after + 1, (count - after - 1) * sizeof(midgard_bundle));
	midgard_bundle *after_bundle = bundles + after;

	midgard_bundle new = mir_bundle_for_op(ctx, ins);
	memcpy(bundles + after + 1, &new, sizeof(new));
	list_add(&new.instructions[0]->link, &after_bundle->instructions[after_bundle->instruction_count - 1]->link);
	block->quadword_count += midgard_tag_props[new.tag].size;

	return new.instructions[0];
	}

	/* Flip the first-two arguments of a (binary) op. Currently ALU
	* only, no known uses for ldst/tex */

	void
	mir_flip(midgard_instruction *ins)
	{
	unsigned temp = ins->src[0];
	ins->src[0] = ins->src[1];
	ins->src[1] = temp;

	assert(ins->type == TAG_ALU_4);

	temp = ins->src_types[0];
	ins->src_types[0] = ins->src_types[1];
	ins->src_types[1] = temp;

	temp = ins->src_abs[0];
	ins->src_abs[0] = ins->src_abs[1];
	ins->src_abs[1] = temp;

	temp = ins->src_neg[0];
	ins->src_neg[0] = ins->src_neg[1];
	ins->src_neg[1] = temp;

	temp = ins->src_invert[0];
	ins->src_invert[0] = ins->src_invert[1];
	ins->src_invert[1] = temp;

	unsigned temp_swizzle[16];
	memcpy(temp_swizzle, ins->swizzle[0], sizeof(ins->swizzle[0]));
	memcpy(ins->swizzle[0], ins->swizzle[1], sizeof(ins->swizzle[0]));
	memcpy(ins->swizzle[1], temp_swizzle, sizeof(ins->swizzle[0]));
	}

	/* Before squashing, calculate ctx->temp_count just by observing the MIR */

	void
	mir_compute_temp_count(compiler_context *ctx)
	{
	if (ctx->temp_count)
	return;

	unsigned max_dest = 0;

	mir_foreach_instr_global(ctx, ins) {
	if (ins->dest < SSA_FIXED_MINIMUM)
	max_dest = MAX2(max_dest, ins->dest + 1);
	}

	ctx->temp_count = max_dest;
	}