Refactor asm rendering

1 files changed, 157 insertions, 0 deletions

diff --git a/disasm.cpp b/disasm.cpp
new file mode 100644
index 0000000..033349b
--- /dev/null
+++ b/disasm.cpp
@@ -0,0 +1,157 @@
+#include "disasm.h"
+#include "data_buffer.h"
+#include "common.h"
+
+#include <cstdio>
+
+static size_t disasm_verbatim(
+        char *out, size_t out_sz, size_t *instr_sz, uint16_t instr, uint32_t, const DataBuffer &)
+{
+    if (instr_sz) {
+        *instr_sz = kInstructionSizeStepBytes;
+    }
+    return Min(out_sz, snprintf(out, out_sz, "  .short 0x%04x", instr));
+}
+
+static size_t disasm_mfff0_v4e70(
+        char *out, size_t out_sz, size_t *instr_sz, uint16_t instr, uint32_t offset, const DataBuffer &code)
+{
+    if (instr_sz) {
+        *instr_sz = kInstructionSizeStepBytes;
+    }
+    if (instr == 0x4e70) {
+        return Min(out_sz, snprintf(out, out_sz, "  reset"));
+    } else if (instr == 0x4e71) {
+        return Min(out_sz, snprintf(out, out_sz, "  nop"));
+    } else if (instr == 0x4e73) {
+        return Min(out_sz, snprintf(out, out_sz, "  rte"));
+    } else if (instr == 0x4e75) {
+        return Min(out_sz, snprintf(out, out_sz, "  rts"));
+    } else if (instr == 0x4e76) {
+        return Min(out_sz, snprintf(out, out_sz, "  trapv"));
+    } else if (instr == 0x4e77) {
+        return Min(out_sz, snprintf(out, out_sz, "  rtr"));
+    }
+    return disasm_verbatim(out, out_sz, instr_sz, instr, offset, code);
+}
+
+static size_t disasm_jsr(
+        char *out, size_t out_sz, size_t *instr_sz, uint16_t instr, uint32_t offset, const DataBuffer & code)
+{
+    const int addrmode = instr & 0x3f;
+    const int m = (addrmode >> 3) & 0x7;
+    const int xn = addrmode & 0x7;
+    switch (m) {
+    case 0: // 4e80 .. 4e87
+    case 1: // 4e88 .. 4e8f
+        break;
+    case 2: // 4e90 .. 4e97
+        if (instr_sz) {
+            *instr_sz = kInstructionSizeStepBytes;
+        }
+        return Min(out_sz, snprintf(out, out_sz, "  jsr %%a%d@", xn));
+    case 3: // 4e98 .. 4e9f
+    case 4: // 4ea0 .. 4ea7
+        break;
+    case 5: // 4ea8 .. 4eaf, Displacement
+        {
+            if (instr_sz) {
+                *instr_sz = kInstructionSizeStepBytes * 2;
+            }
+            const int16_t dispmt = GetI16BE(code.buffer + offset + kInstructionSizeStepBytes);
+            return Min(out_sz, snprintf(out, out_sz, "  jsr %%a%d@(%d:w)", xn, dispmt));
+        }
+    case 6: // 4eb0 .. 4eb7, Brief Extension Word
+        {
+            if (instr_sz) {
+                *instr_sz = kInstructionSizeStepBytes * 2;
+            }
+            const uint16_t briefext = GetU16BE(code.buffer + offset + kInstructionSizeStepBytes);
+            const char reg = ((briefext >> 15) & 1) ? 'a' : 'd';
+            const int xn2 = (briefext >> 12) & 7;
+            const char size_spec = ((briefext >> 11) & 1) ? 'l' : 'w';
+            const int8_t dispmt = briefext & 0xff;
+            return Min(out_sz, snprintf(
+                        out, out_sz, "  jsr %%a%d@(%d,%%%c%d:%c)",
+                        xn, dispmt, reg, xn2, size_spec));
+        }
+    case 7: // 4eb8 .. 4ebf, some are with Brief Extension Word
+        switch (xn) {
+        case 0: // 4eb8 (xxx).W
+            {
+                if (instr_sz) {
+                    *instr_sz = kInstructionSizeStepBytes * 2;
+                }
+                const int32_t dispmt = GetI16BE(code.buffer + offset + kInstructionSizeStepBytes);
+                return Min(out_sz, snprintf(out, out_sz, "  jsr 0x%x:w", dispmt));
+            }
+        case 1: // 4eb9 (xxx).L
+            {
+                if (instr_sz) {
+                    *instr_sz = kInstructionSizeStepBytes * 3;
+                }
+                const int32_t dispmt = GetI32BE(code.buffer + offset + kInstructionSizeStepBytes);
+                return Min(out_sz, snprintf(out, out_sz, "  jsr 0x%x:l", dispmt));
+            }
+        case 2: // 4eba, Displacement
+            {
+                if (instr_sz) {
+                    *instr_sz = kInstructionSizeStepBytes * 2;
+                }
+                const int16_t dispmt = GetI16BE(code.buffer + offset + kInstructionSizeStepBytes);
+                return Min(out_sz, snprintf(out, out_sz, "  jsr %%pc@(%d:w)", dispmt));
+            }
+        case 3: // 4ebb
+            {
+                if (instr_sz) {
+                    *instr_sz = kInstructionSizeStepBytes * 2;
+                }
+                const uint16_t briefext = GetU16BE(
+                        code.buffer + offset + kInstructionSizeStepBytes);
+                const char reg = ((briefext >> 15) & 1) ? 'a' : 'd';
+                const int xn2 = (briefext >> 12) & 7;
+                const char size_spec = ((briefext >> 11) & 1) ? 'l' : 'w';
+                const int8_t dispmt = briefext & 0xff;
+                return Min(out_sz, snprintf(
+                            out, out_sz, "  jsr %%pc@(%d,%%%c%d:%c)", dispmt, reg, xn2, size_spec));
+            }
+        case 4: // 4ebc
+        case 5: // 4ebd
+        case 6: // 4ebe
+            break;
+        }
+        break;
+    }
+    return disasm_verbatim(out, out_sz, instr_sz, instr, offset, code);
+}
+
+size_t m68k_disasm(
+        char *out, size_t out_sz, size_t *instr_sz, uint16_t instr, uint32_t offset, const DataBuffer &code)
+{
+    if ((instr & 0xfff0) == 0x4e70) {
+        return disasm_mfff0_v4e70(out, out_sz, instr_sz, instr, offset, code);
+    } else if ((instr & 0xffc0) == 0x4e80) {
+        return disasm_jsr(out, out_sz, instr_sz, instr, offset, code);
+    }
+    return disasm_verbatim(out, out_sz, instr_sz, instr, offset, code);
+}
+
+size_t m68k_render_raw_data_comment(
+        char *out, size_t out_sz, uint32_t offset, size_t instr_sz, const DataBuffer &code)
+{
+    size_t overall_sz = Min(out_sz, snprintf(out, out_sz, " |"));
+    for (size_t i = 0; i < instr_sz; i += kInstructionSizeStepBytes)
+    {
+        overall_sz += Min(
+                out_sz - overall_sz,
+                snprintf(
+                    out + overall_sz,
+                    out_sz - overall_sz,
+                    " %04x",
+                    GetU16BE(code.buffer + offset + i)));
+    }
+    overall_sz += Min(
+            out_sz - overall_sz,
+            snprintf(out + overall_sz, out_sz - overall_sz, " @%08x", offset));
+    return overall_sz;
+}