https://git.ruby-lang.org/ruby.git/commit/?id=c04e5188d5

From c04e5188d582a3921f44594e88b29ae96abd82a4 Mon Sep 17 00:00:00 2001
From: Alan Wu <XrXr@u...>
Date: Thu, 18 Mar 2021 09:13:13 -0400
Subject: YJIT: use a flat array for finding codegen functions

Simpler and faster.
---
 yjit_codegen.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/yjit_codegen.c b/yjit_codegen.c
index 02410c04ea..823f30f87f 100644
--- a/yjit_codegen.c
+++ b/yjit_codegen.c
@@ -17,7 +17,7 @@ https://github.com/ruby/ruby/blob/trunk/yjit_codegen.c#L17
 #include "yjit_utils.h"
 
 // Map from YARV opcodes to code generation functions
-static st_table *gen_fns;
+static codegen_fn gen_fns[VM_INSTRUCTION_SIZE] = { NULL };
 
 // Code block into which we write machine code
 static codeblock_t block;
@@ -299,10 +299,11 @@ yjit_gen_block(ctx_t* ctx, block_t* block, rb_execution_context_t* ec) https://github.com/ruby/ruby/blob/trunk/yjit_codegen.c#L299
 
         // Get the current opcode
         int opcode = jit_get_opcode(&jit);
+        RUBY_ASSERT(opcode >= 0 && opcode < VM_INSTRUCTION_SIZE);
 
         // Lookup the codegen function for this instruction
-        codegen_fn gen_fn;
-        if (!rb_st_lookup(gen_fns, opcode, (st_data_t*)&gen_fn)) {
+        codegen_fn gen_fn = gen_fns[opcode];
+        if (!gen_fn) {
             // If we reach an unknown instruction,
             // exit to the interpreter and stop compiling
             yjit_gen_exit(&jit, ctx, cb);
@@ -1819,15 +1820,14 @@ gen_opt_getinlinecache(jitstate_t *jit, ctx_t *ctx) https://github.com/ruby/ruby/blob/trunk/yjit_codegen.c#L1820
     return YJIT_END_BLOCK;
 }
 
-void yjit_reg_op(int opcode, codegen_fn gen_fn)
+static void
+yjit_reg_op(int opcode, codegen_fn gen_fn)
 {
+    RUBY_ASSERT(opcode >= 0 && opcode < VM_INSTRUCTION_SIZE);
     // Check that the op wasn't previously registered
-    st_data_t st_gen;
-    if (rb_st_lookup(gen_fns, opcode, &st_gen)) {
-        rb_bug("op already registered");
-    }
+    RUBY_ASSERT(gen_fns[opcode] == NULL);
 
-    st_insert(gen_fns, (st_data_t)opcode, (st_data_t)gen_fn);
+    gen_fns[opcode] = gen_fn;
 }
 
 void
@@ -1841,9 +1841,6 @@ yjit_init_codegen(void) https://github.com/ruby/ruby/blob/trunk/yjit_codegen.c#L1841
     ocb = &outline_block;
     cb_init(ocb, mem_block + mem_size/2, mem_size/2);
 
-    // Initialize the codegen function table
-    gen_fns = rb_st_init_numtable();
-
     // Map YARV opcodes to the corresponding codegen functions
     yjit_reg_op(BIN(dup), gen_dup);
     yjit_reg_op(BIN(nop), gen_nop);
@@ -1865,8 +1862,6 @@ yjit_init_codegen(void) https://github.com/ruby/ruby/blob/trunk/yjit_codegen.c#L1862
     yjit_reg_op(BIN(opt_and), gen_opt_and);
     yjit_reg_op(BIN(opt_minus), gen_opt_minus);
     yjit_reg_op(BIN(opt_plus), gen_opt_plus);
-
-    // Map branch instruction opcodes to codegen functions
     yjit_reg_op(BIN(opt_getinlinecache), gen_opt_getinlinecache);
     yjit_reg_op(BIN(branchif), gen_branchif);
     yjit_reg_op(BIN(branchunless), gen_branchunless);
-- 
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