https://git.ruby-lang.org/ruby.git/commit/?id=5cf7ccd24a

From 5cf7ccd24a9303b2a591bc0289159517cee6e851 Mon Sep 17 00:00:00 2001
From: Maxime Chevalier-Boisvert <maxime.chevalierboisvert@s...>
Date: Fri, 4 Sep 2020 17:10:11 -0400
Subject: Started porting instruction encoding

---
 ujit_asm.c       | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 ujit_asm.h       | 16 +++++++++----
 ujit_asm_tests.c | 11 +++++++++
 3 files changed, 94 insertions(+), 5 deletions(-)

diff --git a/ujit_asm.c b/ujit_asm.c
index 7ff8792059..bb6ad29a5a 100644
--- a/ujit_asm.c
+++ b/ujit_asm.c
@@ -115,6 +115,52 @@ void cb_write_int(codeblock_t* cb, uint64_t val, size_t num_bits) https://github.com/ruby/ruby/blob/trunk/ujit_asm.c#L115
     }
 }
 
+// Ruby instruction prologue and epilogue functions
+void cb_write_prologue(codeblock_t* cb)
+{
+    for (size_t i = 0; i < sizeof(ujit_pre_call_bytes); ++i)
+        cb_write_byte(cb, ujit_pre_call_bytes[i]);
+}
+
+void cb_write_epilogue(codeblock_t* cb)
+{
+    for (size_t i = 0; i < sizeof(ujit_post_call_bytes); ++i)
+        cb_write_byte(cb, ujit_post_call_bytes[i]);
+}
+
+// Write the REX byte
+void writeREX(
+    codeblock_t* cb,
+    bool w_flag,
+    uint8_t reg_no,
+    uint8_t idx_reg_no,
+    uint8_t rm_reg_no
+)
+{
+    // 0 1 0 0 w r x b
+    // w - 64-bit operand size flag
+    // r - MODRM.reg extension
+    // x - SIB.index extension
+    // b - MODRM.rm or SIB.base extension
+    uint8_t w = w_flag? 1:0;
+    uint8_t r = (reg_no & 8)? 1:0;
+    uint8_t x = (idx_reg_no & 8)? 1:0;
+    uint8_t b = (rm_reg_no & 8)? 1:0;
+
+    // Encode and write the REX byte
+    uint8_t rexByte = 0x40 + (w << 3) + (r << 2) + (x << 1) + (b);
+    cb_write_byte(cb, rexByte);
+}
+
+// Write an opcode byte with an embedded register operand
+/*static void cb_write_opcode(codeblock_t* cb, uint8_t opcode, X86Reg rOpnd)
+{
+    // Write the reg field into the opcode byte
+    uint8_t op_byte = opcode | (rOpnd.regNo & 7);
+    cb_write_byte(cb, op_byte);
+}
+*/
+
 // nop - Noop, one or multiple bytes long
 void nop(codeblock_t* cb, size_t length)
 {
@@ -181,3 +227,29 @@ void nop(codeblock_t* cb, size_t length) https://github.com/ruby/ruby/blob/trunk/ujit_asm.c#L227
         break;
     }
 }
+
+/*
+/// push - Push a register on the stack
+void push(codeblock_t* cb, X86Reg reg)
+{
+    assert (reg.size is 64, "can only push 64-bit registers");
+
+    //cb.writeASM("push", reg);
+
+    if (reg.rexNeeded)
+        cb_write_rex(cb, false, 0, 0, reg.regNo);
+    cb_write_byte(cb, 0x50, reg);
+}
+
+/// pop - Pop a register off the stack
+void pop(codeblock_t* cb, X86Reg reg)
+{
+    assert (reg.size is 64);
+
+    //cb.writeASM("pop", reg);
+
+    if (reg.rexNeeded)
+        cb_write_rex(false, 0, 0, reg.regNo);
+    cb_write_byte(cb, 0x58, reg);
+}
+*/
diff --git a/ujit_asm.h b/ujit_asm.h
index 998c171d5d..b192588c69 100644
--- a/ujit_asm.h
+++ b/ujit_asm.h
@@ -51,17 +51,23 @@ typedef struct CodeBlock https://github.com/ruby/ruby/blob/trunk/ujit_asm.h#L51
 
 } codeblock_t;
 
+typedef struct X86Opnd
+{
+
+
+
+
+} x86opnd_t;
+
 void cb_init(codeblock_t* cb, size_t mem_size);
 uint8_t* cb_get_ptr(codeblock_t* cb, size_t index);
 void cb_write_byte(codeblock_t* cb, uint8_t byte);
 void cb_write_bytes(codeblock_t* cb, size_t num_bytes, ...);
 void cb_write_int(codeblock_t* cb, uint64_t val, size_t num_bits);
 
-// TODO:
-// prologue and epilogue functions
-// cb_write_prologue()
-// cb_write_epilogue
-// Test those out
+// Ruby instruction prologue and epilogue functions
+void cb_write_prologue(codeblock_t* cb);
+void cb_write_epilogue(codeblock_t* cb);
 
 void nop(codeblock_t* cb, size_t length);
 
diff --git a/ujit_asm_tests.c b/ujit_asm_tests.c
index 0c94fb8b04..fc8005e56e 100644
--- a/ujit_asm_tests.c
+++ b/ujit_asm_tests.c
@@ -5,6 +5,14 @@ https://github.com/ruby/ruby/blob/trunk/ujit_asm_tests.c#L5
 //fprintf(stderr, format);
 //exit(-1)
 
+// TODO: make a macro to test encoding sequences
+// ***You can use sizeof to know the length***
+// CHECK_BYTES(cb, {})
+
+
+
+
+
 void run_tests()
 {
     printf("Running assembler tests\n");
@@ -12,6 +20,9 @@ void run_tests() https://github.com/ruby/ruby/blob/trunk/ujit_asm_tests.c#L20
     codeblock_t cb;
     cb_init(&cb, 4096);
 
+    cb_write_prologue(&cb);
+    cb_write_epilogue(&cb);
+
 
 
 
-- 
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