From 29fce1d26b395f3a82f757ea37f4c53da8fbde11 Mon Sep 17 00:00:00 2001
From: Gabe Black <gabeblack@google.com>
Date: Mon, 4 Nov 2019 15:02:04 -0800
Subject: [PATCH] cpu: Use std::array for registers in SimpleThread.

If the number of one of the register types is zero (useful on ARM in
the near future), memset will complain that it's given the length of
the array without multiplying by the size of the array elements. This
is a false positive since the length of the array and the number of
elements are both zero.

To avoid that warning/error and to simplify and update the SimpleThread
class slightly, this change replaces the C style arrays with
std::array.

Change-Id: Ifedd081a1940a578765c4d585e623236008ace67
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22523
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---
 src/cpu/simple_thread.hh | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/src/cpu/simple_thread.hh b/src/cpu/simple_thread.hh
index 3a7c85a90..033a0777a 100644
--- a/src/cpu/simple_thread.hh
+++ b/src/cpu/simple_thread.hh
@@ -45,6 +45,8 @@
 #ifndef __CPU_SIMPLE_THREAD_HH__
 #define __CPU_SIMPLE_THREAD_HH__
 
+#include <array>
+
 #include "arch/decoder.hh"
 #include "arch/generic/tlb.hh"
 #include "arch/isa.hh"
@@ -103,12 +105,12 @@ class SimpleThread : public ThreadState, public ThreadContext
     typedef ThreadContext::Status Status;
 
   protected:
-    RegVal floatRegs[TheISA::NumFloatRegs];
-    RegVal intRegs[TheISA::NumIntRegs];
-    VecRegContainer vecRegs[TheISA::NumVecRegs];
-    VecPredRegContainer vecPredRegs[TheISA::NumVecPredRegs];
+    std::array<RegVal, TheISA::NumFloatRegs> floatRegs;
+    std::array<RegVal, TheISA::NumIntRegs> intRegs;
+    std::array<VecRegContainer, TheISA::NumVecRegs> vecRegs;
+    std::array<VecPredRegContainer, TheISA::NumVecPredRegs> vecPredRegs;
 #ifdef ISA_HAS_CC_REGS
-    RegVal ccRegs[TheISA::NumCCRegs];
+    std::array<RegVal, TheISA::NumCCRegs> ccRegs;
 #endif
     TheISA::ISA *const isa;    // one "instance" of the current ISA.
 
@@ -287,19 +289,18 @@ class SimpleThread : public ThreadState, public ThreadContext
 
     void copyArchRegs(ThreadContext *tc) override;
 
-    void clearArchRegs() override
+    void
+    clearArchRegs() override
     {
         _pcState = 0;
-        memset(intRegs, 0, sizeof(intRegs));
-        memset(floatRegs, 0, sizeof(floatRegs));
-        for (int i = 0; i < TheISA::NumVecRegs; i++) {
-            vecRegs[i].zero();
-        }
-        for (int i = 0; i < TheISA::NumVecPredRegs; i++) {
-            vecPredRegs[i].reset();
-        }
+        intRegs.fill(0);
+        floatRegs.fill(0);
+        for (auto &vec_reg: vecRegs)
+            vec_reg.zero();
+        for (auto &pred_reg: vecPredRegs)
+            pred_reg.reset();
 #ifdef ISA_HAS_CC_REGS
-        memset(ccRegs, 0, sizeof(ccRegs));
+        ccRegs.fill(0);
 #endif
         isa->clear();
     }
-- 
2.30.2