From 82cc71261d3d32012d33d3bebe56ca5e3b0bcdbd Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Sun, 2 Oct 2022 15:32:49 -0700
Subject: Initial commit.

---
 isa/isa.h | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 isa/isa.h

(limited to 'isa/isa.h')

diff --git a/isa/isa.h b/isa/isa.h
new file mode 100644
index 0000000..3effb5b
--- /dev/null
+++ b/isa/isa.h
@@ -0,0 +1,44 @@
+#pragma once
+
+#include <functional>
+#include <optional>
+
+#include "infra/pipetrace.h"
+
+enum class ctlreg {
+    DATA_INSTRUCTION_FIELD_BUFFER,  // (df << 3) | if_buffer
+    DATA_INSTRUCTION_FIELD_SAVED,   // (df_saved << 3) | if_saved
+    INT_ENABLE,                     // (int_enable_delay << 1) | int_enable
+};
+
+struct instruction_context {
+    infra::transaction transaction;
+
+    // Known statically at decode time
+    bool need_indirect_load = false;    // final_address = mem[init_address]
+    bool need_autoinc_store = false;    // mem[init_address] += 1
+    bool need_exec_load = false;        // data = mem[final_address]
+    bool need_read_acc = false;         // acc = %acc
+    bool need_read_link = false;        // link = %link
+    std::optional<ctlreg> read_ctlreg;  // ctlval = %[read_ctlreg]
+    bool need_write_acc = false;        // %acc = acc
+    bool need_write_link = false;       // %link = link
+    std::optional<ctlreg> write_ctlreg; // %[write_ctlreg] = ctlval
+    bool need_exec_store = false;       // mem[final_address] = data
+    bool possibly_redirects = false;    // %pc = next_pc
+
+    std::function<void(instruction_context &ctx)> ef;
+    void execute() { ef(*this); }
+
+    // May change over the lifetime of the instruction execution
+    unsigned int next_pc;                       // includes IF
+    std::optional<unsigned int> init_address;   // includes DF
+    std::optional<unsigned int> final_address;  // includes DF
+    std::optional<unsigned int> ctlval;
+    std::optional<unsigned int> data;
+    std::optional<unsigned int> acc;
+    std::optional<bool> link;
+    bool halt = false;
+};
+
+instruction_context decode(unsigned int df, unsigned int pc, unsigned int bits);
-- 
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