YJIT: Use 2D array to group block versions

For deferred compilation, we sometimes want to care about the order of
the block versions. Use an array instead of a linked list to do that.

darray.h

@@ -60,6 +60,11 @@
 #define rb_darray_foreach(ary, idx_name, elem_ptr_var) \
     for (int idx_name = 0; idx_name < rb_darray_size(ary) && ((elem_ptr_var) = rb_darray_ref(ary, idx_name)); ++idx_name)
 
+// Iterate over valid indicies in the array in a for loop
+//
+#define rb_darray_for(ary, idx_name) \
+    for (int idx_name = 0; idx_name < rb_darray_size(ary); ++idx_name)
+
 // Make a dynamic array of a certain size. All bytes backing the elements are set to zero.
 // Return 1 on success and 0 on failure.
 //

ujit_core.c

@@ -144,6 +144,7 @@ int ctx_diff(const ctx_t* src, const ctx_t* dst)
     return diff;
 }
 
+// Get all blocks for a particular place in an iseq.
 static rb_ujit_block_array_t
 get_version_array(const rb_iseq_t *iseq, unsigned idx)
 {
@@ -189,19 +190,14 @@ add_block_version(blockid_t blockid, block_t* block)
 #endif
     }
 
-    block_t *first_version = get_first_version(iseq, blockid.idx);
+    RUBY_ASSERT((int32_t)blockid.idx < rb_darray_size(body->ujit_blocks));
+    rb_ujit_block_array_t *block_array_ref = rb_darray_ref(body->ujit_blocks, blockid.idx);
 
-    // If there exists a version for this block id
-    if (first_version != NULL) {
-        // Link to the next version in a linked list
-        RUBY_ASSERT(block->next == NULL);
-        block->next = first_version;
+    // Add the new block
+    if (!rb_darray_append(block_array_ref, block)) {
+        rb_bug("allocation failed");
     }
 
-    // Make new block the first version
-    rb_darray_set(body->ujit_blocks, blockid.idx, block);
-    RUBY_ASSERT(find_block_version(blockid, &block->ctx) != NULL);
-
     {
         // By writing the new block to the iseq, the iseq now
         // contains new references to Ruby objects. Run write barriers.
@@ -225,17 +221,16 @@ add_block_version(blockid_t blockid, block_t* block)
 // Retrieve a basic block version for an (iseq, idx) tuple
 block_t* find_block_version(blockid_t blockid, const ctx_t* ctx)
 {
-    rb_ujit_block_array_t versions = get_version_array(iseq, block->blockid.idx);
+    rb_ujit_block_array_t versions = get_version_array(blockid.iseq, blockid.idx);
 
     // Best match found
     block_t* best_version = NULL;
     int best_diff = INT_MAX;
 
     // For each version matching the blockid
-    block_t **element;
-    rb_darray_foreach(versions, idx, element) {
-        block_t *version = *element;
-        int diff = ctx_diff(ctx, version->ctx);
+    rb_darray_for(versions, idx) {
+        block_t *version = rb_darray_get(versions, idx);
+        int diff = ctx_diff(ctx, &version->ctx);
 
         // Note that we always prefer the first matching
         // version because of inline-cache chains
@@ -649,21 +644,20 @@ ujit_free_block(block_t *block)
 static bool
 block_array_remove(rb_ujit_block_array_t block_array, block_t *block)
 {
+    bool after_target = false;
     block_t **element;
-    bool shifting = false;
     rb_darray_foreach(block_array, idx, element) {
-        if (*element == block) {
-            shifting = true;
-        }
-        else if (shifting) {
+        if (after_target) {
             rb_darray_set(block_array, idx - 1, *element);
         }
+        else if (*element == block) {
+            after_target = true;
+        }
     }
 
-    if (shifting) {
-        rb_darray_pop(block_array);
-    }
-    return shifting;
+    if (after_target) rb_darray_pop_back(block_array);
+
+    return after_target;
 }
 
 // Invalidate one specific block version
@@ -677,7 +671,6 @@ invalidate_block_version(block_t* block)
 
     // Remove this block from the version array
     rb_ujit_block_array_t versions = get_version_array(iseq, block->blockid.idx);
-    RUBY_ASSERT(rb_darray_size(versions) > 0);
     RB_UNUSED_VAR(bool removed);
     removed = block_array_remove(versions, block);
     RUBY_ASSERT(removed);
@@ -736,7 +729,7 @@ invalidate_block_version(block_t* block)
     // Should check how it's used in exit and side-exit
     const void * const *handler_table = rb_vm_get_insns_address_table();
     void* handler_addr = (void*)handler_table[entry_opcode];
-    iseq->body->iseq_encoded[idx] = (VALUE)handler_addr;    
+    iseq->body->iseq_encoded[idx] = (VALUE)handler_addr;
 
     // TODO:
     // May want to recompile a new entry point (for interpreter entry blocks)

ujit_iface.c

@@ -381,11 +381,13 @@ ujit_blocks_for(VALUE mod, VALUE rb_iseq)
     const rb_iseq_t *iseq = rb_iseqw_to_iseq(rb_iseq);
 
     VALUE all_versions = rb_ary_new();
-    rb_ujit_block_array_t *versions;
-    rb_darray_foreach(iseq->body->ujit_blocks, idx, versions) {
-        block_t **block;
-        rb_darray_foreach(*versions, idx, block) {
-            VALUE rb_block = TypedData_Wrap_Struct(cUjitBlock, &ujit_block_type, *block);
+    rb_darray_for(iseq->body->ujit_blocks, version_array_idx) {
+        rb_ujit_block_array_t versions = rb_darray_get(iseq->body->ujit_blocks, version_array_idx);
+
+        rb_darray_for(versions, block_idx) {
+            block_t *block = rb_darray_get(versions, block_idx);
+
+            VALUE rb_block = TypedData_Wrap_Struct(cUjitBlock, &ujit_block_type, block);
             rb_ary_push(all_versions, rb_block);
         }
     }
@@ -678,12 +680,12 @@ print_ujit_stats(void)
 void
 rb_ujit_iseq_mark(const struct rb_iseq_constant_body *body)
 {
-    block_t **element;
-    rb_darray_foreach(body->ujit_blocks, idx, element) {
+    rb_darray_for(body->ujit_blocks, version_array_idx) {
+        rb_ujit_block_array_t version_array = rb_darray_get(body->ujit_blocks, version_array_idx);
 
+        rb_darray_for(version_array, block_idx) {
+            block_t *block = rb_darray_get(version_array, block_idx);
 
-
-        for (block_t *block = *element; block; block = block->next) {
             rb_gc_mark_movable((VALUE)block->blockid.iseq);
             rb_gc_mark_movable(block->dependencies.cc);
             rb_gc_mark_movable(block->dependencies.cme);
@@ -706,9 +708,12 @@ rb_ujit_iseq_mark(const struct rb_iseq_constant_body *body)
 void
 rb_ujit_iseq_update_references(const struct rb_iseq_constant_body *body)
 {
-    block_t **element;
-    rb_darray_foreach(body->ujit_blocks, idx, element) {
-        for (block_t *block = *element; block; block = block->next) {
+    rb_darray_for(body->ujit_blocks, version_array_idx) {
+        rb_ujit_block_array_t version_array = rb_darray_get(body->ujit_blocks, version_array_idx);
+
+        rb_darray_for(version_array, block_idx) {
+            block_t *block = rb_darray_get(version_array, block_idx);
+
             block->blockid.iseq = (const rb_iseq_t *)rb_gc_location((VALUE)block->blockid.iseq);
 
             block->dependencies.cc = rb_gc_location(block->dependencies.cc);
@@ -736,14 +741,15 @@ rb_ujit_iseq_update_references(const struct rb_iseq_constant_body *body)
 void
 rb_ujit_iseq_free(const struct rb_iseq_constant_body *body)
 {
-    block_t **element;
-    rb_darray_foreach(body->ujit_blocks, idx, element) {
-        block_t *block = *element;
-        while (block) {
-            block_t *next = block->next;
+    rb_darray_for(body->ujit_blocks, version_array_idx) {
+        rb_ujit_block_array_t version_array = rb_darray_get(body->ujit_blocks, version_array_idx);
+
+        rb_darray_for(version_array, block_idx) {
+            block_t *block = rb_darray_get(version_array, block_idx);
             ujit_free_block(block);
-            block = next;
         }
+
+        rb_darray_free(version_array);
     }
 
     rb_darray_free(body->ujit_blocks);