X86: Split Condition Code register

This patch moves the ECF and EZF bits to individual registers (ecfBit and
ezfBit) and the CF and OF bits to cfofFlag registers. This is being done
so as to lower the read after write dependencies on the the condition code
register. Ultimately we will have the following registers [ZAPS], [OF],
[CF], [ECF], [EZF] and [DF]. Note that this is only one part of the
solution for lowering the dependencies. The other part will check whether
or not the condition code register needs to be actually read. This would
be done through a separate patch.

1 files changed, 8 insertions, 5 deletions

diff --git a/src/arch/x86/isa/microops/mediaop.isa b/src/arch/x86/isa/microops/mediaop.isa
index 0c4827990..7178f1f52 100644
--- a/src/arch/x86/isa/microops/mediaop.isa
+++ b/src/arch/x86/isa/microops/mediaop.isa
@@ -1490,12 +1490,15 @@ let {{
             // Less than      0  0  1
             // Equal          1  0  0
             //           OF = SF = AF = 0
-            ccFlagBits = ccFlagBits & ~(OFBit | SFBit | AFBit |
-                                        ZFBit | PFBit | CFBit);
-            if (std::isnan(arg1) || std::isnan(arg2))
-                ccFlagBits = ccFlagBits | (ZFBit | PFBit | CFBit);
+            ccFlagBits = ccFlagBits & ~(SFBit | AFBit | ZFBit | PFBit);
+            cfofBits   = cfofBits   & ~(OFBit | CFBit);
+
+            if (std::isnan(arg1) || std::isnan(arg2)) {
+                ccFlagBits = ccFlagBits | (ZFBit | PFBit);
+                cfofBits = cfofBits | CFBit;
+            }
             else if(arg1 < arg2)
-                ccFlagBits = ccFlagBits | CFBit;
+                cfofBits = cfofBits | CFBit;
             else if(arg1 == arg2)
                 ccFlagBits = ccFlagBits | ZFBit;
         '''