From f6e63892b41ac11577c652bcbd2b20206a9e4f69 Mon Sep 17 00:00:00 2001
From: Seth Morabito <web@loomcom.com>
Date: Thu, 23 Nov 2017 17:07:08 -0800
Subject: [PATCH] 3b2: Preserve opcode values in history

---
 3B2/3b2_cpu.c  | 42 ++++++++++++++++++++++++------------------
 3B2/3b2_defs.h |  2 +-
 3B2/3b2_sys.c  |  4 ++--
 3 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/3B2/3b2_cpu.c b/3B2/3b2_cpu.c
index edd06337..4eacb2ed 100644
--- a/3B2/3b2_cpu.c
+++ b/3B2/3b2_cpu.c
@@ -45,8 +45,8 @@ uint32 *RAM = NULL;
 jmp_buf save_env;
 volatile uint32 abort_context;
 
-/* The last decoded instruction */
-instr cpu_instr;
+/* Pointer to the last decoded instruction */
+instr *cpu_instr;
 
 /* Circular buffer of instructions */
 instr *INST = NULL;
@@ -1368,6 +1368,8 @@ t_stat sim_instr(void)
     uint32   width, offset;
     t_uint64 mask;
 
+    instr inst;
+
     operand *src1, *src2, *src3, *dst;
 
     stop_reason = 0;
@@ -1497,40 +1499,44 @@ t_stat sim_instr(void)
         R[NUM_PSW] &= ~PSW_TM;
         R[NUM_PSW] |= PSW_TM_MASK;
 
-        /* Decode the instruction */
-        memset(&cpu_instr, 0, sizeof(instr));
-        cpu_ilen = decode_instruction(&cpu_instr);
-
         /* Record the instruction for history */
         if (cpu_hist_size > 0) {
-            /* Shallow copy */
-            INST[cpu_hist_p] = cpu_instr;
-            INST[cpu_hist_p].valid = TRUE;
+            cpu_instr = &INST[cpu_hist_p];
             cpu_hist_p = (cpu_hist_p + 1) % cpu_hist_size;
+        } else {
+            cpu_instr = &inst;
         }
 
+        /* Decode the instruction */
+        memset(cpu_instr, 0, sizeof(instr));
+        cpu_ilen = decode_instruction(cpu_instr);
+
+        /* Make sure to update the valid bit for history keeping (if
+         * enabled) */
+        cpu_instr->valid = TRUE;
+
         /*
          * Operate on the decoded instruction.
          */
 
         /* Get the operands */
-        if (cpu_instr.mn->src_op1 >= 0) {
-            src1 = &cpu_instr.operands[cpu_instr.mn->src_op1];
+        if (cpu_instr->mn->src_op1 >= 0) {
+            src1 = &cpu_instr->operands[cpu_instr->mn->src_op1];
         }
 
-        if (cpu_instr.mn->src_op2 >= 0) {
-            src2 = &cpu_instr.operands[cpu_instr.mn->src_op2];
+        if (cpu_instr->mn->src_op2 >= 0) {
+            src2 = &cpu_instr->operands[cpu_instr->mn->src_op2];
         }
 
-        if (cpu_instr.mn->src_op3 >= 0) {
-            src3 = &cpu_instr.operands[cpu_instr.mn->src_op3];
+        if (cpu_instr->mn->src_op3 >= 0) {
+            src3 = &cpu_instr->operands[cpu_instr->mn->src_op3];
         }
 
-        if (cpu_instr.mn->dst_op >= 0) {
-            dst = &cpu_instr.operands[cpu_instr.mn->dst_op];
+        if (cpu_instr->mn->dst_op >= 0) {
+            dst = &cpu_instr->operands[cpu_instr->mn->dst_op];
         }
 
-        switch (cpu_instr.mn->opcode) {
+        switch (cpu_instr->mn->opcode) {
         case ADDW2:
         case ADDH2:
         case ADDB2:
diff --git a/3B2/3b2_defs.h b/3B2/3b2_defs.h
index 7eee2fc6..4d1fc795 100644
--- a/3B2/3b2_defs.h
+++ b/3B2/3b2_defs.h
@@ -53,7 +53,7 @@ noret __libc_longjmp (jmp_buf buf, int val);
 /* -v flag for examine routine */
 #define EX_V_FLAG 1 << 21
 
-#define MAX_HIST_SIZE  1000000
+#define MAX_HIST_SIZE  10000000
 #define MIN_HIST_SIZE  64
 #define MAXMEMSIZE     (1 << 22)             /* 4 MB */
 #define MEM_SIZE       (cpu_unit.capac)      /* actual memory size */
diff --git a/3B2/3b2_sys.c b/3B2/3b2_sys.c
index 986ea394..5ae8704c 100644
--- a/3B2/3b2_sys.c
+++ b/3B2/3b2_sys.c
@@ -45,7 +45,7 @@ REG *sim_PC = &cpu_reg[0];
    there may be up to 3 operands, for a maximum of 20 bytes */
 int32 sim_emax = 20;
 
-extern instr cpu_instr;
+extern instr *cpu_instr;
 
 DEVICE *sim_devices[] = {
     &cpu_dev,
@@ -153,7 +153,7 @@ t_stat fprint_sym(FILE *of, t_addr addr, t_value *val, UNIT *uptr, int32 sw)
     }
 
     if (sw & (int32) SWMASK('M')) {
-        fprint_sym_m(of, &cpu_instr);
+        fprint_sym_m(of, cpu_instr);
         return SCPE_OK;
     }