Mesa (main): nir/lower_shader_calls: put inserted instructions into a dummy block
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Mon May 9 09:30:48 UTC 2022
Module: Mesa
Branch: main
Commit: 35d82ecf1ee117bef575731100fa6ae532f225fc
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=35d82ecf1ee117bef575731100fa6ae532f225fc
Author: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Date: Wed Apr 20 10:51:48 2022 +0300
nir/lower_shader_calls: put inserted instructions into a dummy block
When moving code into the main block or loop blocks, put the code into
its own :
if(true) { ... }
block so that we avoid break/continue/return issues.
v2: Also take care of the main block with return instructions
v3: Make deletion more obvious with dummy if blocks (Jason)
v4: Fixup assert for loops (Lionel)
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Fixes: 8dfb240b1f06 ("nir: Add raytracing shader call lowering pass.")
Reviewed-by: Jason Ekstrand <jason.ekstrand at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16036>
---
src/compiler/nir/nir_lower_shader_calls.c | 74 +++++++++++++++++++++++++------
1 file changed, 61 insertions(+), 13 deletions(-)
diff --git a/src/compiler/nir/nir_lower_shader_calls.c b/src/compiler/nir/nir_lower_shader_calls.c
index 155ba35e932..d6d16a56e34 100644
--- a/src/compiler/nir/nir_lower_shader_calls.c
+++ b/src/compiler/nir/nir_lower_shader_calls.c
@@ -866,8 +866,24 @@ flatten_resume_if_ladder(nir_builder *b,
}
case nir_cf_node_if: {
- assert(!before_cursor);
nir_if *_if = nir_cf_node_as_if(child);
+
+ /* Because of the dummy blocks inserted in the first if block of the
+ * loops, it's possible we find an empty if block that contains our
+ * cursor. At this point, the block should still be empty and we can
+ * just skip it and consider we're after the cursor.
+ */
+ if (cf_node_contains_block(&_if->cf_node,
+ nir_cursor_current_block(b->cursor))) {
+ /* Some sanity checks to verify this is actually a dummy block */
+ assert(nir_src_as_bool(_if->condition) == true);
+ assert(nir_cf_list_is_empty_block(&_if->then_list));
+ assert(nir_cf_list_is_empty_block(&_if->else_list));
+ before_cursor = false;
+ break;
+ }
+ assert(!before_cursor);
+
if (flatten_resume_if_ladder(b, &_if->cf_node, &_if->then_list,
false, resume_instr, remat)) {
resume_node = child;
@@ -900,17 +916,26 @@ flatten_resume_if_ladder(nir_builder *b,
nir_block *header = nir_loop_first_block(loop);
nir_if *_if = nir_cf_node_as_if(nir_cf_node_next(&header->cf_node));
- /* We want to place anything re-materialized from inside the loop
- * at the top of the resume half of the loop.
- */
nir_builder bl;
nir_builder_init(&bl, b->impl);
bl.cursor = nir_before_cf_list(&_if->then_list);
+ /* We want to place anything re-materialized from inside the loop
+ * at the top of the resume half of the loop.
+ *
+ * Because we're inside a loop, we might run into a break/continue
+ * instructions. We can't place those within a block of
+ * instructions, they need to be at the end of a block. So we
+ * build our own dummy block to place them.
+ */
+ nir_push_if(&bl, nir_imm_true(&bl));
+ {
+ ASSERTED bool found =
+ flatten_resume_if_ladder(&bl, &_if->cf_node, &_if->then_list,
+ true, resume_instr, remat);
+ assert(found);
+ }
+ nir_pop_if(&bl, NULL);
- ASSERTED bool found =
- flatten_resume_if_ladder(&bl, &_if->cf_node, &_if->then_list,
- true, resume_instr, remat);
- assert(found);
resume_node = child;
goto found_resume;
} else {
@@ -986,7 +1011,23 @@ found_resume:
* cursor. Delete everything else.
*/
if (child_list_contains_cursor) {
- nir_cf_extract(&cf_list, b->cursor, nir_after_cf_list(child_list));
+ /* If the cursor is in child_list, then we're either a loop or function
+ * that contains the cursor. Cursors are always placed in a wrapper if
+ * (true) to deal with break/continue and early returns. We've already
+ * moved everything interesting inside the wrapper if and we want to
+ * remove whatever is left after it.
+ */
+ nir_block *cursor_block = nir_cursor_current_block(b->cursor);
+ nir_if *wrapper_if = nir_cf_node_as_if(cursor_block->cf_node.parent);
+ assert(wrapper_if->cf_node.parent == parent_node);
+ /* The wrapper if blocks are either put into the body of the main
+ * function, or within the resume if block of the loops.
+ */
+ assert(parent_node->type == nir_cf_node_function ||
+ (parent_node->type == nir_cf_node_if &&
+ parent_node->parent->type == nir_cf_node_loop));
+ nir_cf_extract(&cf_list, nir_after_cf_node(&wrapper_if->cf_node),
+ nir_after_cf_list(child_list));
} else {
nir_cf_list_extract(&cf_list, child_list);
}
@@ -1032,10 +1073,15 @@ lower_resume(nir_shader *shader, int call_idx)
nir_builder b;
nir_builder_init(&b, impl);
b.cursor = nir_before_cf_list(&impl->body);
- ASSERTED bool found =
- flatten_resume_if_ladder(&b, &impl->cf_node, &impl->body,
- true, resume_instr, &remat);
- assert(found);
+
+ nir_push_if(&b, nir_imm_true(&b));
+ {
+ ASSERTED bool found =
+ flatten_resume_if_ladder(&b, &impl->cf_node, &impl->body,
+ true, resume_instr, &remat);
+ assert(found);
+ }
+ nir_pop_if(&b, NULL);
ralloc_free(mem_ctx);
@@ -1167,6 +1213,8 @@ nir_lower_shader_calls(nir_shader *shader,
nir_instr *resume_instr = lower_resume(resume_shaders[i], i);
replace_resume_with_halt(resume_shaders[i], resume_instr);
nir_opt_remove_phis(resume_shaders[i]);
+ /* Remove the dummy blocks added by flatten_resume_if_ladder() */
+ nir_opt_if(resume_shaders[i], false);
}
*resume_shaders_out = resume_shaders;
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