From 80d8f3ae48255f786bd4d52a1819ea0c339f6946 Mon Sep 17 00:00:00 2001
From: Jacques Comeaux <jacquesrcomeaux@protonmail.com>
Date: Fri, 23 Aug 2024 19:46:17 -0500
Subject: Add register parser and binary search for opcodes

---
 newasm/optable.s | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 newasm/optable.s

(limited to 'newasm/optable.s')

diff --git a/newasm/optable.s b/newasm/optable.s
new file mode 100644
index 0000000..a063f02
--- /dev/null
+++ b/newasm/optable.s
@@ -0,0 +1,57 @@
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+.type lookup, %function
+.global lookup
+
+// 1 unexpected char
+// 2 unexpected end of input
+
+// input:
+// R0 input string (unboxed)
+
+// output:
+// R0 return code
+// R1 instruction template
+// R2 instruction type
+// R3 special code
+
+lookup:   PUSH    {R4, R5, R6}
+          ADR     R4, op_table// op table base address
+          MOVS    R5, 0       // begin pointer
+          MOVS    R6, 7       // end pointer
+loop:     CMP     R5, R6      // if begin == end then range = 0
+          BEQ     error
+          ADDS    R2, R5, R6  // get sum
+          LSRS    R2, 1       // divide by two
+no_jiggle:LSLS    R3, R2, 3   // times 8 (index to offset)
+          LDR     R1, [R4, R3]// read opcode from optable
+          CMP     R0, R1      // compare opcode to input
+          BLO     lower       // if lower
+          BHI     higher      // if higher
+found:    LSLS    R2, 3       // times 8 (index to offset)
+          ADDS    R4, R2      // select row
+          MOVS    R0, 0       // success return code
+          LDRH    R1, [R4, 4] // get machine code template
+          LDRB    R2, [R4, 6] // get instruction type
+          LDRB    R3, [R4, 7] // get special code
+          POP     {R4, R5, R6}
+          BX      LR          // result in R2
+lower:    MOVS    R6, R2      // update end pointer
+          B       loop
+higher:   ADDS    R5, R2, 1   // update begin pointer
+          B     loop
+error:    MOVS    R0, 1       // return code 1 (not found)
+          POP     {R4, R5, R6}
+          BX      LR
+
+          .align  8
+op_table:
+          .ascii  "ADD3"; .hword 0x1C00;  .byte 0x01, 0x03  // instr type 1, special code 3 (imm width)
+          .ascii  "ADD8"; .hword 0x3000;  .byte 0x02, 0x08  // instr type 2, special code 8 (imm width)
+          .ascii  "ASPI"; .hword 0xB000;  .byte 0x04, 0x07  // instr type 4, special code 7
+          .ascii  "ASRI"; .hword 0x1000;  .byte 0x01, 0x05  // instr type 1, special code 5 (imm width)
+          .ascii  "ADCS"; .hword 0x4140;  .byte 0x00, 0x00  // instr type 0, special code 0
+          .ascii  "ADDS"; .hword 0x1400;  .byte 0x03, 0x00  // instr type 3, special code 0
+          .ascii  "BKPT"; .hword 0xBE00;  .byte 0x04, 0x08  // instr type 4, special code 8
-- 
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