Don't do copy propagation inside loops until after we try
unrolling them.
This helps avoid propagating everything to the phis which
makes loop unrolling more difficult.
For example without this:
loop {
block block_1:
/* preds: block_0 block_4 */
vec1 32 ssa_10 = phi block_0: ssa_5, block_4: ssa_15
vec1 32 ssa_11 = phi block_0: ssa_6, block_4: ssa_17
vec1 32 ssa_12 = phi block_0: ssa_7, block_4: ssa_18
vec1 32 ssa_13 = phi block_0: ssa_8, block_4: ssa_19
vec1 32 ssa_14 = phi block_0: ssa_9, block_4: ssa_20
vec1 32 ssa_15 = iadd ssa_10, ssa_2
vec1 32 ssa_16 = ige ssa_15, ssa_1
/* succs: block_2 block_3 */
if ssa_16 {
block block_2:
/* preds: block_1 */
break
/* succs: block_5 */
} else {
block block_3:
/* preds: block_1 */
/* succs: block_4 */
}
block block_4:
/* preds: block_3 */
vec1 32 ssa_17 = imov ssa_12
vec1 32 ssa_18 = imov ssa_13
vec1 32 ssa_19 = imov ssa_14
vec1 32 ssa_20 = imov ssa_11
/* succs: block_1 */
}
Will end up as:
loop {
/* preds: block_0 block_4 */
block block_1:
vec1 32 ssa_10 = phi block_0: ssa_5, block_4: ssa_15
vec1 32 ssa_11 = phi block_0: ssa_6, block_4: ssa_12
vec1 32 ssa_12 = phi block_0: ssa_7, block_4: ssa_13
vec1 32 ssa_13 = phi block_0: ssa_8, block_4: ssa_14
vec1 32 ssa_14 = phi block_0: ssa_9, block_4: ssa_11
vec1 32 ssa_15 = iadd ssa_10, ssa_2
vec1 32 ssa_16 = ige ssa_15, ssa_1
/* succs: block_2 block_3 */
if ssa_16 {
block block_2:
/* preds: block_1 */
break
/* succs: block_5 */
} else {
block block_3:
/* preds: block_1 */
/* succs: block_4 */
}
block block_4:
/* preds: block_3 */
/* succs: block_1 */
}
---
src/compiler/nir/nir.h | 2 +-
src/compiler/nir/nir_opt_copy_propagate.c | 47 ++++++++++++++++++++-----------
src/mesa/drivers/dri/i965/brw_nir.c | 6 ++--
3 files changed, 35 insertions(+), 20 deletions(-)
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 5e527d8..e3e06b1 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2562,7 +2562,7 @@ bool nir_opt_constant_folding(nir_shader *shader);
bool nir_opt_global_to_local(nir_shader *shader);
-bool nir_copy_prop(nir_shader *shader);
+bool nir_copy_prop(nir_shader *shader, bool prop_loops);
bool nir_opt_cse(nir_shader *shader);
diff --git a/src/compiler/nir/nir_opt_copy_propagate.c
b/src/compiler/nir/nir_opt_copy_propagate.c
index c26e07f..12daeb6 100644
--- a/src/compiler/nir/nir_opt_copy_propagate.c
+++ b/src/compiler/nir/nir_opt_copy_propagate.c
@@ -99,11 +99,14 @@ is_swizzleless_move(nir_alu_instr *instr)
}
static bool
-copy_prop_src(nir_src *src, nir_instr *parent_instr, nir_if *parent_if)
+copy_prop_src(nir_src *src, nir_instr *parent_instr, nir_if *parent_if,
+ bool prop_loops)
{
if (!src->is_ssa) {
- if (src->reg.indirect)
- return copy_prop_src(src->reg.indirect, parent_instr, parent_if);
+ if (src->reg.indirect) {
+ return copy_prop_src(src->reg.indirect, parent_instr, parent_if,
+ prop_loops);
+ }
return false;
}
@@ -125,6 +128,14 @@ copy_prop_src(nir_src *src, nir_instr *parent_instr,
nir_if *parent_if)
if (phi->dest.ssa.num_components !=
alu_instr->src[0].src.ssa->num_components)
return false;
+
+ /* Avoid propagating moves inside a loop into phis which makes
+ * unrolling difficult.
+ */
+ if (!prop_loops) {
+ if (phi->instr.block->cf_node.parent->type == nir_cf_node_loop)
+ return false;
+ }
}
if (parent_instr) {
@@ -140,13 +151,14 @@ copy_prop_src(nir_src *src, nir_instr *parent_instr,
nir_if *parent_if)
}
static bool
-copy_prop_alu_src(nir_alu_instr *parent_alu_instr, unsigned index)
+copy_prop_alu_src(nir_alu_instr *parent_alu_instr, unsigned index,
+ bool prop_loops)
{
nir_alu_src *src = &parent_alu_instr->src[index];
if (!src->src.is_ssa) {
if (src->src.reg.indirect)
return copy_prop_src(src->src.reg.indirect, &parent_alu_instr->instr,
- NULL);
+ NULL, prop_loops);
return false;
}
@@ -195,6 +207,7 @@ copy_prop_alu_src(nir_alu_instr *parent_alu_instr, unsigned
index)
typedef struct {
nir_instr *parent_instr;
+ bool prop_loops;
bool progress;
} copy_prop_state;
@@ -202,25 +215,26 @@ static bool
copy_prop_src_cb(nir_src *src, void *_state)
{
copy_prop_state *state = (copy_prop_state *) _state;
- while (copy_prop_src(src, state->parent_instr, NULL))
+ while (copy_prop_src(src, state->parent_instr, NULL, state->prop_loops))
state->progress = true;
return true;
}
static bool
-copy_prop_instr(nir_instr *instr)
+copy_prop_instr(nir_instr *instr, bool prop_loops)
{
if (instr->type == nir_instr_type_alu) {
nir_alu_instr *alu_instr = nir_instr_as_alu(instr);
bool progress = false;
for (unsigned i = 0; i < nir_op_infos[alu_instr->op].num_inputs; i++)
- while (copy_prop_alu_src(alu_instr, i))
+ while (copy_prop_alu_src(alu_instr, i, prop_loops))
progress = true;
if (!alu_instr->dest.dest.is_ssa && alu_instr->dest.dest.reg.indirect)
- while (copy_prop_src(alu_instr->dest.dest.reg.indirect, instr, NULL))
+ while (copy_prop_src(alu_instr->dest.dest.reg.indirect, instr, NULL,
+ prop_loops))
progress = true;
return progress;
@@ -229,30 +243,31 @@ copy_prop_instr(nir_instr *instr)
copy_prop_state state;
state.parent_instr = instr;
state.progress = false;
+ state.prop_loops = prop_loops;
nir_foreach_src(instr, copy_prop_src_cb, &state);
return state.progress;
}
static bool
-copy_prop_if(nir_if *if_stmt)
+copy_prop_if(nir_if *if_stmt, bool prop_loops)
{
- return copy_prop_src(&if_stmt->condition, NULL, if_stmt);
+ return copy_prop_src(&if_stmt->condition, NULL, if_stmt, prop_loops);
}
static bool
-nir_copy_prop_impl(nir_function_impl *impl)
+nir_copy_prop_impl(nir_function_impl *impl, bool prop_loops)
{
bool progress = false;
nir_foreach_block(block, impl) {
nir_foreach_instr(instr, block) {
- if (copy_prop_instr(instr))
+ if (copy_prop_instr(instr, prop_loops))
progress = true;
}
nir_if *if_stmt = nir_block_get_following_if(block);
- if (if_stmt && copy_prop_if(if_stmt))
+ if (if_stmt && copy_prop_if(if_stmt, prop_loops))
progress = true;
}
@@ -265,12 +280,12 @@ nir_copy_prop_impl(nir_function_impl *impl)
}
bool
-nir_copy_prop(nir_shader *shader)
+nir_copy_prop(nir_shader *shader, bool prop_loops)
{
bool progress = false;
nir_foreach_function(function, shader) {
- if (function->impl && nir_copy_prop_impl(function->impl))
+ if (function->impl && nir_copy_prop_impl(function->impl, prop_loops))
progress = true;
}
diff --git a/src/mesa/drivers/dri/i965/brw_nir.c
b/src/mesa/drivers/dri/i965/brw_nir.c
index 8aec0d3..6122c2a 100644
--- a/src/mesa/drivers/dri/i965/brw_nir.c
+++ b/src/mesa/drivers/dri/i965/brw_nir.c
@@ -374,13 +374,13 @@ nir_optimize(nir_shader *nir, bool is_scalar)
OPT_V(nir_lower_alu_to_scalar);
}
- OPT(nir_copy_prop);
+ OPT(nir_copy_prop, false);
if (is_scalar) {
OPT_V(nir_lower_phis_to_scalar);
}
- OPT(nir_copy_prop);
+ OPT(nir_copy_prop, false);
OPT(nir_opt_dce);
OPT(nir_opt_cse);
OPT(nir_opt_peephole_select);
@@ -495,7 +495,7 @@ brw_postprocess_nir(nir_shader *nir,
OPT(nir_lower_locals_to_regs);
OPT_V(nir_lower_to_source_mods);
- OPT(nir_copy_prop);
+ OPT(nir_copy_prop, true);
OPT(nir_opt_dce);
if (unlikely(debug_enabled)) {
--
2.7.4
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