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nir/constant_folding: fold load_constant intrinsics

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These can appear after loop unrolling.

v2: stylistic changes
v2: replace state->mem_ctx with state->shader
v2: add bounds checking
v3: use nir_intrinsic_range() for bounds checking
v3: fix issue where partially out-of-bounds reads are replaced with undefs
v4: fix merge conflicts during rebase
v5: split into two commits
v6: set constant_data to NULL after freeing (fixes nir_sweep()/Iris)
v7: don't remove the constant data if there are no constant loads

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com> (v6)
Acked-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Rhys Perry 2019-09-04 17:03:18 +01:00
parent ec054a67da
commit 2d78e55a8c
1 changed files with 58 additions and 0 deletions
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58
src/compiler/nir/nir_opt_constant_folding.c
View file

@ -35,6 +35,8 @@
struct constant_fold_state {
nir_shader *shader;
unsigned execution_mode;
bool has_load_constant;
bool has_indirect_load_const;
};
static bool
@ -134,6 +136,50 @@ constant_fold_intrinsic_instr(struct constant_fold_state *state, nir_intrinsic_i
nir_instr_remove(&instr->instr);
progress = true;
}
} else if (instr->intrinsic == nir_intrinsic_load_constant) {
state->has_load_constant = true;
if (!nir_src_is_const(instr->src[0])) {
state->has_indirect_load_const = true;
return progress;
}
unsigned offset = nir_src_as_uint(instr->src[0]);
unsigned base = nir_intrinsic_base(instr);
unsigned range = nir_intrinsic_range(instr);
assert(base + range <= state->shader->constant_data_size);
nir_instr *new_instr = NULL;
if (offset >= range) {
nir_ssa_undef_instr *undef =
nir_ssa_undef_instr_create(state->shader,
instr->num_components,
instr->dest.ssa.bit_size);
nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(&undef->def));
new_instr = &undef->instr;
} else {
nir_load_const_instr *load_const =
nir_load_const_instr_create(state->shader,
instr->num_components,
instr->dest.ssa.bit_size);
uint8_t *data = (uint8_t*)state->shader->constant_data + base;
for (unsigned i = 0; i < instr->num_components; i++) {
unsigned bytes = instr->dest.ssa.bit_size / 8;
bytes = MIN2(bytes, range - offset);
memcpy(&load_const->value[i].u64, data + offset, bytes);
offset += bytes;
}
nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(&load_const->def));
new_instr = &load_const->instr;
}
nir_instr_insert_before(&instr->instr, new_instr);
nir_instr_remove(&instr->instr);
progress = true;
}
return progress;
@ -190,11 +236,23 @@ nir_opt_constant_folding(nir_shader *shader)
struct constant_fold_state state;
state.shader = shader;
state.execution_mode = shader->info.float_controls_execution_mode;
state.has_load_constant = false;
state.has_indirect_load_const = false;
nir_foreach_function(function, shader) {
if (function->impl)
progress |= nir_opt_constant_folding_impl(&state, function->impl);
}
/* This doesn't free the constant data if there are no constant loads because
* the data might still be used but the loads have been lowered to load_ubo
*/
if (state.has_load_constant && !state.has_indirect_load_const &&
shader->constant_data_size) {
ralloc_free(shader->constant_data);
shader->constant_data = NULL;
shader->constant_data_size = 0;
}
return progress;
}