Gabe Black has uploaded this change for review. ( https://gem5-review.googlesource.com/c/public/gem5/+/52071 )

Change subject: cpu-simple: Use a local temporary for the PC in preExecute.
......................................................................

cpu-simple: Use a local temporary for the PC in preExecute.

This avoids having to dynamically allocate and then free a temporary
when working with the pc in preExecute.

Change-Id: Ic86e23d0f0c7e786122a6024a154bb2907a6afcb
---
M src/cpu/simple/base.cc
M src/cpu/simple/base.hh
2 files changed, 24 insertions(+), 9 deletions(-)



diff --git a/src/cpu/simple/base.cc b/src/cpu/simple/base.cc
index 57bdc59..7067f20 100644
--- a/src/cpu/simple/base.cc
+++ b/src/cpu/simple/base.cc
@@ -313,14 +313,15 @@
     t_info.setMemAccPredicate(true);

     // decode the instruction
-    std::unique_ptr<PCStateBase> pc_state(thread->pcState().clone());
+    set(preExecuteTempPC, thread->pcState());
+    auto &pc_state = *preExecuteTempPC;

     auto &decoder = thread->decoder;

-    if (isRomMicroPC(pc_state->microPC())) {
+    if (isRomMicroPC(pc_state.microPC())) {
         t_info.stayAtPC = false;
         curStaticInst = decoder.fetchRomMicroop(
-                pc_state->microPC(), curMacroStaticInst);
+                pc_state.microPC(), curMacroStaticInst);
     } else if (!curMacroStaticInst) {
         //We're not in the middle of a macro instruction
         StaticInstPtr instPtr = NULL;
@@ -328,16 +329,16 @@
         //Predecode, ie bundle up an ExtMachInst
         //If more fetch data is needed, pass it in.
         Addr fetch_pc =
-            (pc_state->instAddr() & decoder.pcMask()) + t_info.fetchOffset;
+            (pc_state.instAddr() & decoder.pcMask()) + t_info.fetchOffset;

-        decoder.moreBytes(*pc_state, fetch_pc);
+        decoder.moreBytes(pc_state, fetch_pc);

         //Decode an instruction if one is ready. Otherwise, we'll have to
         //fetch beyond the MachInst at the current pc.
-        instPtr = decoder.decode(*pc_state);
+        instPtr = decoder.decode(pc_state);
         if (instPtr) {
             t_info.stayAtPC = false;
-            thread->pcState(*pc_state);
+            thread->pcState(pc_state);
         } else {
             t_info.stayAtPC = true;
             t_info.fetchOffset += decoder.moreBytesSize();
@@ -348,13 +349,13 @@
         if (instPtr && instPtr->isMacroop()) {
             curMacroStaticInst = instPtr;
             curStaticInst =
-                curMacroStaticInst->fetchMicroop(pc_state->microPC());
+                curMacroStaticInst->fetchMicroop(pc_state.microPC());
         } else {
             curStaticInst = instPtr;
         }
     } else {
         //Read the next micro op from the macro op
- curStaticInst = curMacroStaticInst->fetchMicroop(pc_state->microPC()); + curStaticInst = curMacroStaticInst->fetchMicroop(pc_state.microPC());
     }

//If we decoded an instruction this "tick", record information about it.
diff --git a/src/cpu/simple/base.hh b/src/cpu/simple/base.hh
index 4e94e5c..b0fdbe3 100644
--- a/src/cpu/simple/base.hh
+++ b/src/cpu/simple/base.hh
@@ -129,6 +129,8 @@
      */
     void traceFault();

+    std::unique_ptr<PCStateBase> preExecuteTempPC;
+
   public:
     void checkForInterrupts();
     void setupFetchRequest(const RequestPtr &req);

--
To view, visit https://gem5-review.googlesource.com/c/public/gem5/+/52071
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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: Ic86e23d0f0c7e786122a6024a154bb2907a6afcb
Gerrit-Change-Number: 52071
Gerrit-PatchSet: 1
Gerrit-Owner: Gabe Black <gabe.bl...@gmail.com>
Gerrit-MessageType: newchange
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