From 3cb87f71df753ec08bb8e635ac9016846d67912c Mon Sep 17 00:00:00 2001
From: Andrew Waterman <waterman@cs.berkeley.edu>
Date: Mon, 8 Feb 2016 23:29:41 -0800
Subject: [PATCH] Fix ERET serialization strategy

It was screwing up the commit log.
---
 riscv/decode.h     |  9 ++++++---
 riscv/execute.cc   | 11 +++++++----
 riscv/processor.cc |  2 ++
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/riscv/decode.h b/riscv/decode.h
index f8437ca..f4d6b6c 100644
--- a/riscv/decode.h
+++ b/riscv/decode.h
@@ -200,18 +200,21 @@ private:
 
 #define set_pc_and_serialize(x) \
   do { set_pc(x); /* check alignment */ \
-       npc = PC_SERIALIZE; \
+       npc = PC_SERIALIZE_AFTER; \
        STATE.pc = (x); \
      } while(0)
 
-#define PC_SERIALIZE 3 /* sentinel value indicating simulator pipeline flush */
+/* Sentinel PC values to serialize simulator pipeline */
+#define PC_SERIALIZE_BEFORE 3
+#define PC_SERIALIZE_AFTER 5
+#define invalid_pc(pc) ((pc) & 1)
 
 /* Convenience wrappers to simplify softfloat code sequences */
 #define f32(x) ((float32_t){(uint32_t)x})
 #define f64(x) ((float64_t){(uint64_t)x})
 
 #define validate_csr(which, write) ({ \
-  if (!STATE.serialized) return PC_SERIALIZE; \
+  if (!STATE.serialized) return PC_SERIALIZE_BEFORE; \
   STATE.serialized = false; \
   unsigned csr_priv = get_field((which), 0x300); \
   unsigned csr_read_only = get_field((which), 0xC00) == 3; \
diff --git a/riscv/execute.cc b/riscv/execute.cc
index a2e71a1..014055b 100644
--- a/riscv/execute.cc
+++ b/riscv/execute.cc
@@ -43,7 +43,7 @@ static reg_t execute_insn(processor_t* p, reg_t pc, insn_fetch_t fetch)
 {
   commit_log_stash_privilege(p->get_state());
   reg_t npc = fetch.func(p, fetch.insn, pc);
-  if (npc != PC_SERIALIZE) {
+  if (!invalid_pc(npc)) {
     commit_log_print_insn(p->get_state(), pc, fetch.insn);
     p->update_histogram(pc);
   }
@@ -59,9 +59,13 @@ void processor_t::step(size_t n)
     mmu_t* _mmu = mmu;
 
     #define advance_pc() \
-     if (unlikely(pc == PC_SERIALIZE)) { \
+     if (unlikely(invalid_pc(pc))) { \
+       switch (pc) { \
+         case PC_SERIALIZE_BEFORE: state.serialized = true; break; \
+         case PC_SERIALIZE_AFTER: instret++; break; \
+         default: abort(); \
+       } \
        pc = state.pc; \
-       state.serialized = true; \
        break; \
      } else { \
        state.pc = pc; \
@@ -70,7 +74,6 @@ void processor_t::step(size_t n)
 
     try
     {
-      check_timer();
       take_interrupt();
 
       if (unlikely(debug))
diff --git a/riscv/processor.cc b/riscv/processor.cc
index a79ee7b..1503661 100644
--- a/riscv/processor.cc
+++ b/riscv/processor.cc
@@ -161,6 +161,8 @@ static int ctz(reg_t val)
 
 void processor_t::take_interrupt()
 {
+  check_timer();
+
   reg_t interrupts = state.mip & state.mie;
 
   reg_t m_interrupts = interrupts & ~state.mideleg;
-- 
2.30.2