From 91ed230d8324cded1a5d82cf8f85d9d81af00956 Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Mon, 31 Oct 2022 19:14:05 -0700
Subject: Only use DF for addresses generated via indirection.

---
 isa/checker.cpp | 3 ++-
 isa/decode.cpp  | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

(limited to 'isa')

diff --git a/isa/checker.cpp b/isa/checker.cpp
index 770d9d6..6eaa15f 100644
--- a/isa/checker.cpp
+++ b/isa/checker.cpp
@@ -21,7 +21,8 @@ void checker::execute() {
             addr = (addr + 1) & 07777;
             mem.store(*inst.init_address, addr);
         }
-        inst.final_address = addr;
+        auto df = ctlregs[DATA_INSTRUCTION_FIELD_BUFFER] >> 3;
+        inst.final_address = (df << 12) | addr;
     } else {
         assert(!inst.need_autoinc_store);
     }
diff --git a/isa/decode.cpp b/isa/decode.cpp
index af38c64..f183c1f 100644
--- a/isa/decode.cpp
+++ b/isa/decode.cpp
@@ -373,7 +373,7 @@ instruction_context decode(unsigned int dfifb, unsigned int pc, unsigned int bit
 
     // Instructions with memory operands may be direct or indirect
     if (inst.need_exec_load || inst.need_exec_store || inst.possibly_redirects) {
-        auto addr = (df << 12) | ((bits & 00200) ? (pc & 07600) : 0) | (bits & 00177);
+        auto addr = (pc & 070000) | ((bits & 00200) ? (pc & 07600) : 0) | (bits & 00177);
         if (bits & 00400) {
             inst.need_indirect_load = true;
             inst.init_address = addr;
-- 
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