https://git.ruby-lang.org/ruby.git/commit/?id=f7717b1d46

From f7717b1d463548414e607498e84815ac641ce3dc Mon Sep 17 00:00:00 2001
From: Maxime Chevalier-Boisvert <maxime.chevalierboisvert@s...>
Date: Thu, 10 Dec 2020 00:06:10 -0500
Subject: Start refactoring JIT engine

---
 ujit_codegen.c | 14 +++++---------
 ujit_codegen.h |  2 +-
 ujit_core.c    | 42 ++++++++++++++++++++++++++++++++++++------
 ujit_core.h    | 20 ++++++++++++++------
 ujit_iface.c   | 22 +++++-----------------
 5 files changed, 61 insertions(+), 39 deletions(-)

diff --git a/ujit_codegen.c b/ujit_codegen.c
index 03b72ec2c3..c51f7b1944 100644
--- a/ujit_codegen.c
+++ b/ujit_codegen.c
@@ -43,7 +43,7 @@ static void https://github.com/ruby/ruby/blob/trunk/ujit_codegen.c#L43
 ujit_gen_exit(codeblock_t* cb, ctx_t* ctx, VALUE* exit_pc)
 {
     // Write the adjusted SP back into the CFP
-    if (ctx->stack_diff != 0)
+    if (ctx->stack_size != 0)
     {
         x86opnd_t stack_pointer = ctx_sp_opnd(ctx, 0);
         lea(cb, REG_SP, stack_pointer);
@@ -95,11 +95,10 @@ ujit_side_exit(codeblock_t* cb, ctx_t* ctx, VALUE* exit_pc) https://github.com/ruby/ruby/blob/trunk/ujit_codegen.c#L95
 
 /*
 Compile a sequence of bytecode instructions starting at `insn_idx`.
-Return the index to the first instruction not compiled in the sequence
-through `next_ujit_idx`. Return `NULL` in case compilation fails.
+Returns `NULL` if compilation fails.
 */
 uint8_t *
-ujit_compile_insn(const rb_iseq_t *iseq, unsigned int insn_idx, unsigned int *next_ujit_idx)
+ujit_compile_block(const rb_iseq_t *iseq, unsigned int insn_idx)
 {
     assert (cb != NULL);
     unsigned first_insn_idx = insn_idx;
@@ -174,16 +173,13 @@ ujit_compile_insn(const rb_iseq_t *iseq, unsigned int insn_idx, unsigned int *ne https://github.com/ruby/ruby/blob/trunk/ujit_codegen.c#L173
         }
     }
 
-    // Let the caller know how many instructions ujit compiled
-    *next_ujit_idx = insn_idx;
-
     // If no instructions were compiled
     if (num_instrs == 0) {
         return NULL;
     }
 
     // Generate code to exit to the interpreter
-    ujit_gen_exit(cb, &ctx, &encoded[*next_ujit_idx]);
+    ujit_gen_exit(cb, &ctx, &encoded[insn_idx]);
 
     map_addr2insn(code_ptr, first_opcode);
 
@@ -191,7 +187,7 @@ ujit_compile_insn(const rb_iseq_t *iseq, unsigned int insn_idx, unsigned int *ne https://github.com/ruby/ruby/blob/trunk/ujit_codegen.c#L187
         // Dump list of compiled instrutions
         fprintf(stderr, "Compiled the following for iseq=%p:\n", (void *)iseq);
         VALUE *pc = &encoded[first_insn_idx];
-        VALUE *end_pc = &encoded[*next_ujit_idx];
+        VALUE *end_pc = &encoded[insn_idx];
         while (pc < end_pc) {
             int opcode = opcode_at_pc(iseq, pc);
             fprintf(stderr, "  %04td %s\n", pc - encoded, insn_name(opcode));
diff --git a/ujit_codegen.h b/ujit_codegen.h
index a6667b01df..7c03420097 100644
--- a/ujit_codegen.h
+++ b/ujit_codegen.h
@@ -3,7 +3,7 @@ https://github.com/ruby/ruby/blob/trunk/ujit_codegen.h#L3
 
 #include "stddef.h"
 
-uint8_t * ujit_compile_insn(const rb_iseq_t *iseq, unsigned int insn_idx, unsigned int *next_ujit_idx);
+uint8_t * ujit_compile_block(const rb_iseq_t *iseq, unsigned int insn_idx);
 
 void ujit_init_codegen(void);
 
diff --git a/ujit_core.c b/ujit_core.c
index 5ac6407219..261a33315f 100644
--- a/ujit_core.c
+++ b/ujit_core.c
@@ -1,7 +1,37 @@ https://github.com/ruby/ruby/blob/trunk/ujit_core.c#L1
+#include "internal.h"
 #include "ujit_asm.h"
 #include "ujit_iface.h"
 #include "ujit_core.h"
 
+
+
+
+// Table of block versions indexed by (iseq, index) tuples
+st_table * version_tbl;
+
+/*
+struct st_hash_type {
+    int (*compare)(st_data_t, st_data_t); // st_compare_func*
+    st_index_t (*hash)(st_data_t);        // st_hash_func*
+};
+
+static const struct st_hash_type st_hashtype_num = {
+    st_numcmp,
+    st_numhash,
+};
+
+strcasehash(st_data_t arg)
+{
+    register const char *string = (const char *)arg;
+    ...
+}
+
+*/
+
+
+
+
+
 // Get the current instruction opcode from the context object
 int
 ctx_get_opcode(ctx_t *ctx)
@@ -23,7 +53,7 @@ Get an operand for the adjusted stack pointer address https://github.com/ruby/ruby/blob/trunk/ujit_core.c#L53
 x86opnd_t
 ctx_sp_opnd(ctx_t* ctx, int32_t offset_bytes)
 {
-    int32_t offset = (ctx->stack_diff) * 8 + offset_bytes;
+    int32_t offset = (ctx->stack_size) * 8 + offset_bytes;
     return mem_opnd(64, REG_SP, offset);
 }
 
@@ -34,10 +64,10 @@ Return a pointer to the new stack top https://github.com/ruby/ruby/blob/trunk/ujit_core.c#L64
 x86opnd_t
 ctx_stack_push(ctx_t* ctx, size_t n)
 {
-    ctx->stack_diff += n;
+    ctx->stack_size += n;
 
     // SP points just above the topmost value
-    int32_t offset = (ctx->stack_diff - 1) * 8;
+    int32_t offset = (ctx->stack_size - 1) * 8;
     return mem_opnd(64, REG_SP, offset);
 }
 
@@ -49,10 +79,10 @@ x86opnd_t https://github.com/ruby/ruby/blob/trunk/ujit_core.c#L79
 ctx_stack_pop(ctx_t* ctx, size_t n)
 {
     // SP points just above the topmost value
-    int32_t offset = (ctx->stack_diff - 1) * 8;
+    int32_t offset = (ctx->stack_size - 1) * 8;
     x86opnd_t top = mem_opnd(64, REG_SP, offset);
 
-    ctx->stack_diff -= n;
+    ctx->stack_size -= n;
 
     return top;
 }
@@ -61,7 +91,7 @@ x86opnd_t https://github.com/ruby/ruby/blob/trunk/ujit_core.c#L91
 ctx_stack_opnd(ctx_t* ctx, int32_t idx)
 {
     // SP points just above the topmost value
-    int32_t offset = (ctx->stack_diff - 1 - idx) * 8;
+    int32_t offset = (ctx->stack_size - 1 - idx) * 8;
     x86opnd_t opnd = mem_opnd(64, REG_SP, offset);
 
     return opnd;
diff --git a/ujit_core.h b/ujit_core.h
index ede28e7834..320be8fa01 100644
--- a/ujit_core.h
+++ b/ujit_core.h
@@ -17,16 +17,18 @@ https://github.com/ruby/ruby/blob/trunk/ujit_core.h#L17
 #define REG0_32 EAX
 #define REG1_32 ECX
 
+// Maximum number of versions per block
+#define MAX_VERSIONS 5
+
 // Code generation context
 typedef struct ctx_struct
 {
-    // Current PC
-    VALUE *pc;
-
-    // Difference between the current stack pointer and actual stack top
-    int32_t stack_diff;
+    // TODO: we may want to remove information that is not
+    // strictly necessary for versioning from this struct
+    // Some of the information here is only needed during
+    // code generation, eg: current pc
 
-    // The iseq that owns the region that is compiling
+    // Instruction sequence this is associated with
     const rb_iseq_t *iseq;
 
     // Index in the iseq of the opcode we are replacing
@@ -35,6 +37,12 @@ typedef struct ctx_struct https://github.com/ruby/ruby/blob/trunk/ujit_core.h#L37
     // The start of the generated code
     uint8_t *code_ptr;
 
+    // Current PC
+    VALUE *pc;
+
+    // Number of values pushed on the temporary stack
+    int32_t stack_size;
+
     // Whether we know self is a heap object
     bool self_is_object;
 
diff --git a/ujit_iface.c b/ujit_iface.c
index 404c75dbee..ac541b7cdc 100644
--- a/ujit_iface.c
+++ b/ujit_iface.c
@@ -232,25 +232,13 @@ rb_ujit_compile_iseq(const rb_iseq_t *iseq) https://github.com/ruby/ruby/blob/trunk/ujit_iface.c#L232
     RB_VM_LOCK_ENTER();
     VALUE *encoded = (VALUE *)iseq->body->iseq_encoded;
 
-    unsigned int insn_idx;
-    unsigned int next_ujit_idx = 0;
+    // Compile a block version starting at the first instruction
+    uint8_t* native_code_ptr = ujit_compile_block(iseq, 0);
 
-    for (insn_idx = 0; insn_idx < iseq->body->iseq_size; /* */) {
-        int insn = opcode_at_pc(iseq, &encoded[insn_idx]);
-        int len = insn_len(insn);
-
-        uint8_t *native_code_ptr = NULL;
-
-        // If ujit hasn't already compiled this instruction
-        if (insn_idx >= next_ujit_idx) {
-            native_code_ptr = ujit_compile_insn(iseq, insn_idx, &next_ujit_idx);
-        }
-
-        if (native_code_ptr) {
-            encoded[insn_idx] = (VALUE)native_code_ptr;
-        }
-        insn_idx += len;
+    if (native_code_ptr) {
+        encoded[0] = (VALUE)native_code_ptr;
     }
+
     RB_VM_LOCK_LEAVE();
 #endif
 }
-- 
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