check loads using tainted registers, set USL dst as tainted

5 files changed, 52 insertions, 2 deletions

diff --git a/src/cpu/base_dyn_inst.hh b/src/cpu/base_dyn_inst.hh
index 4d8014445..756a5aa9f 100644
--- a/src/cpu/base_dyn_inst.hh
+++ b/src/cpu/base_dyn_inst.hh
@@ -480,11 +480,22 @@ class BaseDynInst : public ExecContext, public RefCounted
 
     void taintDestRegs(void)
     {
-        for (auto dstreg: _destRegIdx) {
+        for (size_t i = 0; i < numDestRegs(); i++) {
+            auto dstreg = _destRegIdx[i];
             cpu->setTaint(dstreg);
         }
     }
 
+    bool srcTainted(void)
+    {
+        bool result = false;
+        for (size_t i = 0; i < numSrcRegs(); i++) {
+            auto src = _srcRegIdx[i];
+            result |= cpu->regTainted(src);
+        }
+        return result;
+    }
+
     /** Renames a source logical register to the physical register which
      *  has/will produce that logical register's result.
      *  @todo: add in whether or not the source register is ready.
diff --git a/src/cpu/o3/cpu.cc b/src/cpu/o3/cpu.cc
index 2566cf12a..ad4e6d549 100644
--- a/src/cpu/o3/cpu.cc
+++ b/src/cpu/o3/cpu.cc
@@ -1286,6 +1286,13 @@ FullO3CPU<Impl>::setTaint(PhysRegIdPtr phys_reg)
 }
 
 template <class Impl>
+bool
+FullO3CPU<Impl>::regTainted(PhysRegIdPtr phys_reg)
+{
+    return regFile.regTainted(phys_reg);
+}
+
+template <class Impl>
 uint64_t
 FullO3CPU<Impl>::readIntReg(PhysRegIdPtr phys_reg)
 {
diff --git a/src/cpu/o3/cpu.hh b/src/cpu/o3/cpu.hh
index 23e6f7434..131655ecd 100644
--- a/src/cpu/o3/cpu.hh
+++ b/src/cpu/o3/cpu.hh
@@ -401,6 +401,7 @@ class FullO3CPU : public BaseO3CPU
 
     /** taint a register */
     void setTaint(PhysRegIdPtr phys_reg);
+    bool regTainted(PhysRegIdPtr phys_reg);
 
     uint64_t readIntReg(PhysRegIdPtr phys_reg);
 
diff --git a/src/cpu/o3/lsq_unit_impl.hh b/src/cpu/o3/lsq_unit_impl.hh
index 7462d4c84..14256e382 100644
--- a/src/cpu/o3/lsq_unit_impl.hh
+++ b/src/cpu/o3/lsq_unit_impl.hh
@@ -1043,6 +1043,7 @@ LSQUnit<Impl>::updateVisibleState()
                 }
                 inst->readyToExpose(true);
             }else {
+#if 0 /* now an untainted USL can be safe */
                 if (inst->readyToExpose()){
                     DPRINTF(LSQUnit, "The load can not be validated "
                             "[sn:%lli] PC %s\n",
@@ -1050,7 +1051,19 @@ LSQUnit<Impl>::updateVisibleState()
                     assert(0);
                     //--loadsToVLD;
                 }
-                inst->readyToExpose(false);
+#endif
+                /* set taint for dst registers */
+                inst->taintDestRegs();
+                /* if the load depends on tainted registers, set
+                   readyToExpose to false, otherwise set it to true
+                */
+                if (inst->srcTainted()) {
+                    DPRINTF(LSQUnit, "load inst [sn:%lli] %s not safe, set readyToExpose to false\n", inst->seqNum, inst->pcState());
+                    inst->readyToExpose(false);
+                } else {
+                    DPRINTF(LSQUnit, "load inst [sn:%lli] %s is an unsafe speculated load, but source registers are not tainted.\n", inst->seqNum, inst->pcState());
+                    inst->readyToExpose(true);
+                }
             }
             inst->fenceDelay(false);
         } else {
diff --git a/src/cpu/o3/regfile.hh b/src/cpu/o3/regfile.hh
index 00b4ef045..4d54acc2f 100644
--- a/src/cpu/o3/regfile.hh
+++ b/src/cpu/o3/regfile.hh
@@ -199,10 +199,28 @@ class PhysRegFile
         miscTaintMap[idx] = true;
         break;
       default:
+        warn_once("taint for vector registers not supported yet\n");
         break;
       }
     }
 
+    bool regTainted(PhysRegIdPtr phys_reg) {
+      RegIndex idx = phys_reg->index();
+      switch (phys_reg->classValue()) {
+      case IntRegClass:
+        return intTaintMap[idx];
+      case FloatRegClass:
+        return floatTaintMap[idx];
+      case CCRegClass:
+        return ccTaintMap[idx];
+      case MiscRegClass:
+        return miscTaintMap[idx];
+      default:
+        warn_once("taint for vector registers not supported yet\n");
+        return false;
+      }
+    }
+
     /** Reads an integer register. */
     uint64_t readIntReg(PhysRegIdPtr phys_reg) const
     {