x86: Adjust the size of the values written to the x87 misc registers

All x87 misc registers are implemented in an array of 64 bit values
but in real hardware the size of some of these registers is smaller.
Previsouly all 64 bits where incorrectly set and then later read.  To
ensure correctness we mask the value in setMiscRegNoEffect to write
only the valid bits.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>

1 files changed, 49 insertions, 10 deletions

diff --git a/src/arch/x86/isa.cc b/src/arch/x86/isa.cc
index f2d3ce42a..f9b99db0f 100644
--- a/src/arch/x86/isa.cc
+++ b/src/arch/x86/isa.cc
@@ -129,11 +129,13 @@ ISA::readMiscRegNoEffect(int miscReg) const
     // Make sure we're not dealing with an illegal control register.
     // Instructions should filter out these indexes, and nothing else should
     // attempt to read them directly.
-    assert( miscReg != MISCREG_CR1 &&
-            !(miscReg > MISCREG_CR4 &&
-              miscReg < MISCREG_CR8) &&
-            !(miscReg > MISCREG_CR8 &&
-              miscReg <= MISCREG_CR15));
+    assert(miscReg >= MISCREG_CR0 &&
+           miscReg < NUM_MISCREGS &&
+           miscReg != MISCREG_CR1 &&
+           !(miscReg > MISCREG_CR4 &&
+             miscReg < MISCREG_CR8) &&
+           !(miscReg > MISCREG_CR8 &&
+             miscReg <= MISCREG_CR15));
 
     return regVal[miscReg];
 }
@@ -160,11 +162,48 @@ ISA::setMiscRegNoEffect(int miscReg, MiscReg val)
     // Make sure we're not dealing with an illegal control register.
     // Instructions should filter out these indexes, and nothing else should
     // attempt to write to them directly.
-    assert( miscReg != MISCREG_CR1 &&
-            !(miscReg > MISCREG_CR4 &&
-              miscReg < MISCREG_CR8) &&
-            !(miscReg > MISCREG_CR8 &&
-              miscReg <= MISCREG_CR15));
+    assert(miscReg >= MISCREG_CR0 &&
+           miscReg < NUM_MISCREGS &&
+           miscReg != MISCREG_CR1 &&
+           !(miscReg > MISCREG_CR4 &&
+             miscReg < MISCREG_CR8) &&
+           !(miscReg > MISCREG_CR8 &&
+             miscReg <= MISCREG_CR15));
+
+    HandyM5Reg m5Reg = readMiscRegNoEffect(MISCREG_M5_REG);
+    switch (miscReg) {
+      case MISCREG_FSW:
+        val &= (1ULL << 16) - 1;
+        regVal[miscReg] = val;
+        miscReg = MISCREG_X87_TOP;
+        val <<= 11;
+      case MISCREG_X87_TOP:
+        val &= (1ULL << 3) - 1;
+        break;
+      case MISCREG_FTW:
+        val &= (1ULL << 8) - 1;
+        break;
+      case MISCREG_FCW:
+      case MISCREG_FOP:
+        val &= (1ULL << 16) - 1;
+        break;
+      case MISCREG_MXCSR:
+        val &= (1ULL << 32) - 1;
+        break;
+      case MISCREG_FISEG:
+      case MISCREG_FOSEG:
+        if (m5Reg.submode != SixtyFourBitMode)
+            val &= (1ULL << 16) - 1;
+        break;
+      case MISCREG_FIOFF:
+      case MISCREG_FOOFF:
+        if (m5Reg.submode != SixtyFourBitMode)
+            val &= (1ULL << 32) - 1;
+        break;
+      default:
+        break;
+    }
+
     regVal[miscReg] = val;
 }