intel/compiler: Add the ability to defer IP updates in backend_instruction::remove

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11632>

src/intel/compiler/brw_cfg.cpp

@@ -63,7 +63,7 @@ push_stack(exec_list *list, void *mem_ctx, bblock_t *block)
 }
 
 bblock_t::bblock_t(cfg_t *cfg) :
-   cfg(cfg), start_ip(0), end_ip(0), num(0)
+   cfg(cfg), start_ip(0), end_ip(0), end_ip_delta(0), num(0)
 {
    instructions.make_empty();
    parents.make_empty();

src/intel/compiler/brw_cfg.h

@@ -115,6 +115,11 @@ struct bblock_t {
    int start_ip;
    int end_ip;
 
+   /**
+    * Change in end_ip since the last time IPs of later blocks were updated.
+    */
+   int end_ip_delta;
+
    struct exec_list instructions;
    struct exec_list parents;
    struct exec_list children;

src/intel/compiler/brw_ir.h

@@ -107,7 +107,7 @@ struct backend_instruction : public exec_node {
     */
    bool uses_indirect_addressing() const;
 
-   void remove(bblock_t *block);
+   void remove(bblock_t *block, bool defer_later_block_ip_updates = false);
    void insert_after(bblock_t *block, backend_instruction *inst);
    void insert_before(bblock_t *block, backend_instruction *inst);
    void insert_before(bblock_t *block, exec_list *list);

src/intel/compiler/brw_shader.cpp

@@ -1196,6 +1196,7 @@ void
 backend_instruction::insert_after(bblock_t *block, backend_instruction *inst)
 {
    assert(this != inst);
+   assert(block->end_ip_delta == 0);
 
    if (!this->is_head_sentinel())
       assert(inst_is_in_block(block, this) || !"Instruction not in block");
@@ -1211,6 +1212,7 @@ void
 backend_instruction::insert_before(bblock_t *block, backend_instruction *inst)
 {
    assert(this != inst);
+   assert(block->end_ip_delta == 0);
 
    if (!this->is_tail_sentinel())
       assert(inst_is_in_block(block, this) || !"Instruction not in block");
@@ -1226,6 +1228,7 @@ void
 backend_instruction::insert_before(bblock_t *block, exec_list *list)
 {
    assert(inst_is_in_block(block, this) || !"Instruction not in block");
+   assert(block->end_ip_delta == 0);
 
    unsigned num_inst = list->length();
 
@@ -1237,13 +1240,23 @@ backend_instruction::insert_before(bblock_t *block, exec_list *list)
 }
 
 void
-backend_instruction::remove(bblock_t *block)
+backend_instruction::remove(bblock_t *block, bool defer_later_block_ip_updates)
 {
    assert(inst_is_in_block(block, this) || !"Instruction not in block");
 
-   adjust_later_block_ips(block, -1);
+   if (defer_later_block_ip_updates) {
+      block->end_ip_delta--;
+   } else {
+      assert(block->end_ip_delta == 0);
+      adjust_later_block_ips(block, -1);
+   }
 
    if (block->start_ip == block->end_ip) {
+      if (block->end_ip_delta != 0) {
+         adjust_later_block_ips(block, block->end_ip_delta);
+         block->end_ip_delta = 0;
+      }
+
       block->cfg->remove_block(block);
    } else {
       block->end_ip--;