X-Git-Url: https://git.libre-soc.org/?a=blobdiff_plain;f=src%2Fglsl%2Fnir%2Fnir_control_flow.h;h=b71382fc5977566077f14187076988f0b9e2a054;hb=e16531fbe3a79bc27cf00701616a260b452597ef;hp=5a3be260f63005bcf5fb535f876377a9302ead1f;hpb=476eb5e4a16efdbc54c4418e44b1f38989026add;p=mesa.git diff --git a/src/glsl/nir/nir_control_flow.h b/src/glsl/nir/nir_control_flow.h index 5a3be260f63..b71382fc597 100644 --- a/src/glsl/nir/nir_control_flow.h +++ b/src/glsl/nir/nir_control_flow.h @@ -37,97 +37,14 @@ extern "C" { * * This file contains various API's that make modifying control flow in NIR, * while maintaining the invariants checked by the validator, much easier. + * There are two parts to this: + * + * 1. Inserting control flow (if's and loops) in various places, for creating + * IR either from scratch or as part of some lowering pass. + * 2. Taking existing pieces of the IR and either moving them around or + * deleting them. */ -/* Helper struct for representing a point to extract/insert. Helps reduce the - * combinatorial explosion of possible points to extract. - */ - -typedef enum { - nir_cursor_before_block, - nir_cursor_after_block, - nir_cursor_before_instr, - nir_cursor_after_instr, -} nir_cursor_option; - -typedef struct { - nir_cursor_option option; - union { - nir_block *block; - nir_instr *instr; - }; -} nir_cursor; - -static inline nir_cursor -nir_before_block(nir_block *block) -{ - nir_cursor cursor; - cursor.option = nir_cursor_before_block; - cursor.block = block; - return cursor; -} - -static inline nir_cursor -nir_after_block(nir_block *block) -{ - nir_cursor cursor; - cursor.option = nir_cursor_after_block; - cursor.block = block; - return cursor; -} - -static inline nir_cursor -nir_before_instr(nir_instr *instr) -{ - nir_cursor cursor; - cursor.option = nir_cursor_before_instr; - cursor.instr = instr; - return cursor; -} - -static inline nir_cursor -nir_after_instr(nir_instr *instr) -{ - nir_cursor cursor; - cursor.option = nir_cursor_after_instr; - cursor.instr = instr; - return cursor; -} - -static inline nir_cursor -nir_before_cf_node(nir_cf_node *node) -{ - if (node->type == nir_cf_node_block) - return nir_before_block(nir_cf_node_as_block(node)); - - return nir_after_block(nir_cf_node_as_block(nir_cf_node_prev(node))); -} - -static inline nir_cursor -nir_after_cf_node(nir_cf_node *node) -{ - if (node->type == nir_cf_node_block) - return nir_after_block(nir_cf_node_as_block(node)); - - return nir_before_block(nir_cf_node_as_block(nir_cf_node_next(node))); -} - -static inline nir_cursor -nir_before_cf_list(struct exec_list *cf_list) -{ - nir_cf_node *first_node = exec_node_data(nir_cf_node, - exec_list_get_head(cf_list), node); - return nir_before_cf_node(first_node); -} - -static inline nir_cursor -nir_after_cf_list(struct exec_list *cf_list) -{ - nir_cf_node *last_node = exec_node_data(nir_cf_node, - exec_list_get_tail(cf_list), node); - return nir_after_cf_node(last_node); -} - /** Control flow insertion. */ /** puts a control flow node where the cursor is */ @@ -161,8 +78,84 @@ nir_cf_node_insert_end(struct exec_list *list, nir_cf_node *node) nir_cf_node_insert(nir_after_cf_list(list), node); } + +/** Control flow motion. + * + * These functions let you take a part of a control flow list (basically + * equivalent to a series of statement in GLSL) and "extract" it from the IR, + * so that it's a free-floating piece of IR that can be either re-inserted + * somewhere else or deleted entirely. A few notes on using it: + * + * 1. Phi nodes are considered attached to the piece of control flow that + * their sources come from. There are three places where phi nodes can + * occur, which are the three places where a block can have multiple + * predecessors: + * + * 1) After an if statement, if neither branch ends in a jump. + * 2) After a loop, if there are multiple break's. + * 3) At the beginning of a loop. + * + * For #1, the phi node is considered to be part of the if, and for #2 and + * #3 the phi node is considered to be part of the loop. This allows us to + * keep phi's intact, but it means that phi nodes cannot be separated from + * the control flow they come from. For example, extracting an if without + * extracting all the phi nodes after it is not allowed, and neither is + * extracting only some of the phi nodes at the beginning of a block. It + * also means that extracting from the beginning of a basic block actually + * means extracting from the first non-phi instruction, since there's no + * situation where extracting phi nodes without extracting what comes + * before them makes any sense. + * + * 2. Phi node sources are guaranteed to remain valid, meaning that they still + * correspond one-to-one with the predecessors of the basic block they're + * part of. In addition, the original sources will be preserved unless they + * correspond to a break or continue that was deleted. However, no attempt + * is made to ensure that SSA form is maintained. In particular, it is + * *not* guaranteed that definitions of SSA values will dominate all their + * uses after all is said and done. Either the caller must ensure that this + * is the case, or it must insert extra phi nodes to restore SSA. + * + * 3. It is invalid to move a piece of IR with a break/continue outside of the + * loop it references. Doing this will result in invalid + * successors/predecessors and phi node sources. + * + * 4. It is invalid to move a piece of IR from one function implementation to + * another. + * + * 5. Extracting a control flow list will leave lots of dangling references to + * and from other pieces of the IR. It also leaves things in a not 100% + * consistent state. This means that some things (e.g. inserting + * instructions) might not work reliably on the extracted control flow. It + * also means that extracting control flow without re-inserting it or + * deleting it is a Bad Thing (tm). + */ + +typedef struct { + struct exec_list list; + nir_function_impl *impl; /* for cleaning up if the list is deleted */ +} nir_cf_list; + +void nir_cf_extract(nir_cf_list *extracted, nir_cursor begin, nir_cursor end); + +void nir_cf_reinsert(nir_cf_list *cf_list, nir_cursor cursor); + +void nir_cf_delete(nir_cf_list *cf_list); + +static inline void +nir_cf_list_extract(nir_cf_list *extracted, struct exec_list *cf_list) +{ + nir_cf_extract(extracted, nir_before_cf_list(cf_list), + nir_after_cf_list(cf_list)); +} + /** removes a control flow node, doing any cleanup necessary */ -void nir_cf_node_remove(nir_cf_node *node); +static inline void +nir_cf_node_remove(nir_cf_node *node) +{ + nir_cf_list list; + nir_cf_extract(&list, nir_before_cf_node(node), nir_after_cf_node(node)); + nir_cf_delete(&list); +} #ifdef __cplusplus }