From ea70e6d6daee29e7a4780d4b48f8140220ee2576 Mon Sep 17 00:00:00 2001
From: Gabe Black <gblack@eecs.umich.edu>
Date: Tue, 19 Jun 2007 18:17:34 +0000
Subject: [PATCH] Make branches work by repopulating the predecoder every time
 through. This is probably fine as far as the predecoder goes, but the simple
 cpu might want to not refetch something it already has. That reintroduces the
 self modifying code problem though.

--HG--
extra : convert_revision : 802197e65f8dc1ad657c6b346091e03cb563b0c0
---
 src/arch/alpha/predecoder.hh |  6 +-----
 src/arch/mips/predecoder.hh  |  3 +--
 src/arch/sparc/predecoder.hh |  4 +---
 src/arch/x86/predecoder.hh   |  6 +++---
 src/cpu/o3/fetch_impl.hh     |  2 +-
 src/cpu/simple/atomic.cc     |  6 +++---
 src/cpu/simple/base.cc       | 10 +++++-----
 7 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/src/arch/alpha/predecoder.hh b/src/arch/alpha/predecoder.hh
index 0407ce99b..4887de856 100644
--- a/src/arch/alpha/predecoder.hh
+++ b/src/arch/alpha/predecoder.hh
@@ -44,8 +44,6 @@ namespace AlphaISA
     {
       protected:
         ThreadContext * tc;
-        //The pc of the current instruction
-        Addr fetchPC;
         //The extended machine instruction being generated
         ExtMachInst ext_inst;
 
@@ -69,10 +67,8 @@ namespace AlphaISA
 
         //Use this to give data to the predecoder. This should be used
         //when there is control flow.
-        void moreBytes(Addr pc, Addr _fetchPC, Addr off, MachInst inst)
+        void moreBytes(Addr pc, Addr fetchPC, MachInst inst)
         {
-            fetchPC = _fetchPC;
-            assert(off == 0);
             ext_inst = inst;
 #if FULL_SYSTEM
             if (pc && 0x1)
diff --git a/src/arch/mips/predecoder.hh b/src/arch/mips/predecoder.hh
index 90f768d73..e310dded4 100644
--- a/src/arch/mips/predecoder.hh
+++ b/src/arch/mips/predecoder.hh
@@ -66,9 +66,8 @@ namespace MipsISA
 
         //Use this to give data to the predecoder. This should be used
         //when there is control flow.
-        void moreBytes(Addr pc, Addr fetchPC, Addr off, MachInst inst)
+        void moreBytes(Addr pc, Addr fetchPC, MachInst inst)
         {
-            assert(off == 0);
             emi = inst;
         }
 
diff --git a/src/arch/sparc/predecoder.hh b/src/arch/sparc/predecoder.hh
index 38d8fd1a2..d990c3256 100644
--- a/src/arch/sparc/predecoder.hh
+++ b/src/arch/sparc/predecoder.hh
@@ -67,10 +67,8 @@ namespace SparcISA
 
         //Use this to give data to the predecoder. This should be used
         //when there is control flow.
-        void moreBytes(Addr pc, Addr fetchPC, Addr off, MachInst inst)
+        void moreBytes(Addr pc, Addr fetchPC, MachInst inst)
         {
-            assert(off == 0);
-
             emi = inst;
             //The I bit, bit 13, is used to figure out where the ASI
             //should come from. Use that in the ExtMachInst. This is
diff --git a/src/arch/x86/predecoder.hh b/src/arch/x86/predecoder.hh
index 3c858f061..f34b66364 100644
--- a/src/arch/x86/predecoder.hh
+++ b/src/arch/x86/predecoder.hh
@@ -195,12 +195,12 @@ namespace X86ISA
 
         //Use this to give data to the predecoder. This should be used
         //when there is control flow.
-        void moreBytes(Addr pc, Addr fetchPC, Addr off, MachInst data)
+        void moreBytes(Addr pc, Addr fetchPC, MachInst data)
         {
+            DPRINTF(Predecoder, "Getting more bytes.\n");
             basePC = fetchPC;
-            offset = off;
+            offset = (fetchPC >= pc) ? 0 : pc - fetchPC;
             fetchChunk = data;
-            assert(off < sizeof(MachInst));
             outOfBytes = false;
             process();
         }
diff --git a/src/cpu/o3/fetch_impl.hh b/src/cpu/o3/fetch_impl.hh
index ab55ec744..1ce5bd20f 100644
--- a/src/cpu/o3/fetch_impl.hh
+++ b/src/cpu/o3/fetch_impl.hh
@@ -1128,7 +1128,7 @@ DefaultFetch<Impl>::fetch(bool &status_change)
                         (&cacheData[tid][offset]));
 
             predecoder.setTC(cpu->thread[tid]->getTC());
-            predecoder.moreBytes(fetch_PC, fetch_PC, 0, inst);
+            predecoder.moreBytes(fetch_PC, fetch_PC, inst);
 
             ext_inst = predecoder.getExtMachInst();
 
diff --git a/src/cpu/simple/atomic.cc b/src/cpu/simple/atomic.cc
index ea1c7d87f..03ff1282b 100644
--- a/src/cpu/simple/atomic.cc
+++ b/src/cpu/simple/atomic.cc
@@ -521,15 +521,15 @@ AtomicSimpleCPU::tick()
             dcache_access = false; // assume no dcache access
 
             //Fetch more instruction memory if necessary
-            if(predecoder.needMoreBytes())
-            {
+            //if(predecoder.needMoreBytes())
+            //{
                 icache_access = true;
                 ifetch_pkt->reinitFromRequest();
 
                 icache_latency = icachePort.sendAtomic(ifetch_pkt);
                 // ifetch_req is initialized to read the instruction directly
                 // into the CPU object's inst field.
-            }
+            //}
 
             preExecute();
 
diff --git a/src/cpu/simple/base.cc b/src/cpu/simple/base.cc
index b7f60522f..9285aa7b5 100644
--- a/src/cpu/simple/base.cc
+++ b/src/cpu/simple/base.cc
@@ -379,11 +379,11 @@ BaseSimpleCPU::preExecute()
         //This should go away once the constructor can be set up properly
         predecoder.setTC(thread->getTC());
         //If more fetch data is needed, pass it in.
-        if(predecoder.needMoreBytes())
-            predecoder.moreBytes(thread->readPC(),
-                    (thread->readPC() & PCMask) + fetchOffset, 0, inst);
-        else
-            predecoder.process();
+        Addr fetchPC = (thread->readPC() & PCMask) + fetchOffset;
+        //if(predecoder.needMoreBytes())
+            predecoder.moreBytes(thread->readPC(), fetchPC, inst);
+        //else
+        //    predecoder.process();
 
         //If an instruction is ready, decode it. Otherwise, we'll have to
         //fetch beyond the MachInst at the current pc.