From eb3fd68203fee7c63245c702914c2acd3332d65a Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Thu, 22 Sep 2022 11:29:07 -0700
Subject: Initial commit.

---
 backend/exec.h | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 backend/exec.h

(limited to 'backend/exec.h')

diff --git a/backend/exec.h b/backend/exec.h
new file mode 100644
index 0000000..f1474b8
--- /dev/null
+++ b/backend/exec.h
@@ -0,0 +1,72 @@
+#pragma once
+
+#include "infra/port.h"
+#include "inst.h"
+#include "memory/dram.h"
+
+namespace backend {
+    struct exec : public infra::sim {
+        infra::port<inst> execp;
+        infra::port<inst> *writebackp = nullptr;
+        infra::port<memory::dram::command> *loadp = nullptr;
+        infra::port<memory::dram::response> loadresultp;
+
+        infra::port<inst> stallp;
+
+        void clock() {
+            if (stallp.can_read() && writebackp->can_write()) {
+                const auto &i = stallp.peek();
+                switch (i.field[OPCODE]) {
+                    case OP_LOAD:
+                        if (loadresultp.can_read()) {
+                            auto i = stallp.read();
+                            auto addr = i.field[SRC1] + i.field[SRC2];
+                            auto offset = addr & memory::LINE_BYTE_OFFSET_MASK;
+                            pte(i.transaction, "", fmt::format("addr={:x} offset={:x}", addr, offset));
+                            auto f = loadresultp.read();
+                            std::uint64_t r = 0;
+                            for (unsigned int i = 0; i < sizeof(r); ++i)
+                                r |= f.data[i + offset] << (8 * i);
+                            i.result = r;
+                            writebackp->write(std::move(i));
+                        }
+                        break;
+                }
+            } else if (execp.can_read() && writebackp->can_write() && loadp->can_write()) {
+                auto i = execp.read();
+                pte(i.transaction, "E", fmt::format("exec gen={} op={:x} a={:x} b={:x}", i.generation, i.field[OPCODE], i.field[SRC1], i.field[SRC2]));
+                switch (i.field[OPCODE]) {
+                    case OP_JUMP_ABS_IF_ZERO:
+                        if (i.field[SRC2] == 0)
+                            i.result = i.field[SRC1];
+                        else
+                            i.result = i.linear_next_pc;
+                        break;
+                    case OP_JUMP_ABS_IF_NONZERO:
+                        if (i.field[SRC2] != 0)
+                            i.result = i.field[SRC1];
+                        else
+                            i.result = i.linear_next_pc;
+                        break;
+                    case OP_EMIT:
+                    case OP_ADD:
+                        i.result = i.field[SRC1] + i.field[SRC2];
+                        break;
+                    case OP_LOAD:
+                        {
+                            memory::dram::command c;
+                            c.transaction = i.transaction;
+                            c.line_address = (i.field[SRC1] + i.field[SRC2]) >> memory::LINE_BYTES_LOG2;
+                            c.write = false;
+                            c.responsep = &loadresultp;
+                            loadp->write(std::move(c));
+                        }
+                        stallp.write(std::move(i));
+                        break;
+                }
+                if (stallp.can_write())
+                    writebackp->write(std::move(i));
+            }
+        }
+    };
+}
-- 
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