mips,cpu: Get rid of the IsIprAccess StaticInst flag.

This was set by MIPS in two places, I think largely just because it was
available. This flag refers to IPRs which are an Alpha concept. In the
O3 CPU, IsIprAccess was used as a possible indicator to determine if an
instruction IsSerializeBefore, but we've already got a flag for that. In
the minor CPU, which hasn't been made to work with MIPS as far as I
know, it was used in a condition but not mentioned in the comment
alongside the condition. I think there it was added for the sake of
Alpha.

This change eliminates that flag and removes it from the O3 and minor
CPUs. In the MIPS ISA description, the instructions that were marked as
IsIprAccess have now been marked as IsSerializeBefore since, if there
was a real reason for them to be marked as IsIprAccess, it would have
been to get it them to work in O3, and there IsSerializeBefore gets
equivalent behavior.

Change-Id: Ia874cde12fa70b998d3e638458f13d69798d40b7
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33739
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>

src/arch/mips/isa/decoder.isa

@@ -174,10 +174,10 @@ decode OPCODE_HI default Unknown::unknown() {
 
             0x2: decode FUNCTION_LO {
                 0x0: HiLoRsSelOp::mfhi({{ Rd = HI_RS_SEL; }},
-                             IntMultOp, IsIprAccess);
+                             IntMultOp, IsSerializeBefore);
                 0x1: HiLoRdSelOp::mthi({{ HI_RD_SEL = Rs; }});
                 0x2: HiLoRsSelOp::mflo({{ Rd = LO_RS_SEL; }},
-                             IntMultOp, IsIprAccess);
+                             IntMultOp, IsSerializeBefore);
                 0x3: HiLoRdSelOp::mtlo({{ LO_RD_SEL = Rs; }});
             }
 

src/cpu/StaticInstFlags.py

@@ -89,7 +89,6 @@ class StaticInstFlags(Enum):
         'IsNonSpeculative', # Should not be executed speculatively
         'IsQuiesce',        # Is a quiesce instruction
 
-        'IsIprAccess',      # Accesses IPRs
         'IsUnverifiable',   # Can't be verified by a checker
 
         'IsSyscall',        # Causes a system call to be emulated in syscall

src/cpu/base_dyn_inst.hh

@@ -557,7 +557,6 @@ class BaseDynInst : public ExecContext, public RefCounted
     bool isWriteBarrier() const { return staticInst->isWriteBarrier(); }
     bool isNonSpeculative() const { return staticInst->isNonSpeculative(); }
     bool isQuiesce() const { return staticInst->isQuiesce(); }
-    bool isIprAccess() const { return staticInst->isIprAccess(); }
     bool isUnverifiable() const { return staticInst->isUnverifiable(); }
     bool isSyscall() const { return staticInst->isSyscall(); }
     bool isMacroop() const { return staticInst->isMacroop(); }

src/cpu/minor/execute.cc

@@ -224,8 +224,7 @@ Execute::tryToBranch(MinorDynInstPtr inst, Fault fault, BranchData &branch)
         !inst->isFault() &&
         inst->isLastOpInInst() &&
         (inst->staticInst->isSerializeAfter() ||
-         inst->staticInst->isSquashAfter() ||
-         inst->staticInst->isIprAccess());
+         inst->staticInst->isSquashAfter());
 
     DPRINTF(Branch, "tryToBranch before: %s after: %s%s\n",
         pc_before, target, (force_branch ? " (forcing)" : ""));

src/cpu/o3/rename_impl.hh

@@ -684,8 +684,7 @@ DefaultRename<Impl>::renameInsts(ThreadID tid)
         // instructions.  This is mainly due to lack of support for
         // out-of-order operations of either of those classes of
         // instructions.
-        if ((inst->isIprAccess() || inst->isSerializeBefore()) &&
-            !inst->isSerializeHandled()) {
+        if (inst->isSerializeBefore() && !inst->isSerializeHandled()) {
             DPRINTF(Rename, "Serialize before instruction encountered.\n");
 
             if (!inst->isTempSerializeBefore()) {

src/cpu/static_inst.hh

@@ -190,7 +190,6 @@ class StaticInst : public RefCounted, public StaticInstFlags
     bool isWriteBarrier() const { return flags[IsWriteBarrier]; }
     bool isNonSpeculative() const { return flags[IsNonSpeculative]; }
     bool isQuiesce() const { return flags[IsQuiesce]; }
-    bool isIprAccess() const { return flags[IsIprAccess]; }
     bool isUnverifiable() const { return flags[IsUnverifiable]; }
     bool isSyscall() const { return flags[IsSyscall]; }
     bool isMacroop() const { return flags[IsMacroop]; }