bpo-43693: Compute deref offsets in compiler (gh-25152)

Merges locals and cells into a single array.
Saves a pointer in the interpreter and means that we don't need the LOAD_CLOSURE opcode any more

https://bugs.python.org/issue43693

1 files changed, 21 insertions, 0 deletions

diff --git a/Python/compile.c b/Python/compile.c
index b0c9f3c..1104250 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -7435,6 +7435,24 @@ guarantee_lineno_for_exits(struct assembler *a, int firstlineno) {
     }
 }
 
+static void
+offset_derefs(basicblock *entryblock, int nlocals)
+{
+    for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
+        for (int i = 0; i < b->b_iused; i++) {
+            struct instr *inst = &b->b_instr[i];
+            switch(inst->i_opcode) {
+                case LOAD_CLOSURE:
+                case LOAD_DEREF:
+                case STORE_DEREF:
+                case DELETE_DEREF:
+                case LOAD_CLASSDEREF:
+                    inst->i_oparg += nlocals;
+            }
+        }
+    }
+}
+
 static PyCodeObject *
 assemble(struct compiler *c, int addNone)
 {
@@ -7490,6 +7508,9 @@ assemble(struct compiler *c, int addNone)
     a.a_entry = entryblock;
     a.a_nblocks = nblocks;
 
+    assert(PyDict_GET_SIZE(c->u->u_varnames) < INT_MAX);
+    offset_derefs(entryblock, (int)PyDict_GET_SIZE(c->u->u_varnames));
+
     consts = consts_dict_keys_inorder(c->u->u_consts);
     if (consts == NULL) {
         goto error;