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authorNilay Vaish <nilay@cs.wisc.edu>2012-09-11 09:33:42 -0500
committerNilay Vaish <nilay@cs.wisc.edu>2012-09-11 09:33:42 -0500
commitf47c2f64156ee031c481af8d1516ada9d19da775 (patch)
tree907e33ee9e8ab4b5a9233a02e946a161ed699297 /src/arch
parent6369df59c85870c0975bc881d7b7d612c9dcf15b (diff)
downloadgem5-f47c2f64156ee031c481af8d1516ada9d19da775.tar.xz
X86: make use of register predication
The patch introduces two predicates for condition code registers -- one tests if a register needs to be read, the other tests whether a register needs to be written to. These predicates are evaluated twice -- during construction of the microop and during its execution. Register reads and writes are elided depending on how the predicates evaluate.
Diffstat (limited to 'src/arch')
-rw-r--r--src/arch/x86/isa/microops/regop.isa287
-rw-r--r--src/arch/x86/isa/operands.isa36
2 files changed, 188 insertions, 135 deletions
diff --git a/src/arch/x86/isa/microops/regop.isa b/src/arch/x86/isa/microops/regop.isa
index a96a552a3..d14ec8aad 100644
--- a/src/arch/x86/isa/microops/regop.isa
+++ b/src/arch/x86/isa/microops/regop.isa
@@ -438,40 +438,43 @@ let {{
flag_code = '''
//Don't have genFlags handle the OF or CF bits
uint64_t mask = CFBit | ECFBit | OFBit;
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~mask, result, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~mask, result, psrc1, op2);
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
//If a logic microop wants to set these, it wants to set them to 0.
- cfofBits = cfofBits & ~((CFBit | OFBit) & ext);
- ecfBit = ecfBit & ~(ECFBit & ext);
+ PredcfofBits = PredcfofBits & ~((CFBit | OFBit) & ext);
+ PredecfBit = PredecfBit & ~(ECFBit & ext);
'''
class FlagRegOp(RegOp):
abstract = True
flag_code = '''
- uint64_t newFlags = genFlags(ccFlagBits | cfofBits | dfBit |
- ecfBit | ezfBit, ext, result, psrc1, op2);
- cfofBits = newFlags & cfofMask;
- ecfBit = newFlags & ECFBit;
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PredcfofBits |
+ PreddfBit | PredecfBit | PredezfBit,
+ ext, result, psrc1, op2);
+
+ PredcfofBits = newFlags & cfofMask;
+ PredecfBit = newFlags & ECFBit;
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
'''
class SubRegOp(RegOp):
abstract = True
flag_code = '''
- uint64_t newFlags = genFlags(ccFlagBits | cfofBits | dfBit |
- ecfBit | ezfBit, ext, result, psrc1,
- ~op2, true);
- cfofBits = newFlags & cfofMask;
- ecfBit = newFlags & ECFBit;
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PredcfofBits |
+ PreddfBit | PredecfBit | PredezfBit,
+ ext, result, psrc1, ~op2, true);
+
+ PredcfofBits = newFlags & cfofMask;
+ PredecfBit = newFlags & ECFBit;
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
'''
class CondRegOp(RegOp):
@@ -556,11 +559,11 @@ let {{
flag_code = '''
if ((-ProdHi & mask(dataSize * 8)) !=
bits(ProdLow, dataSize * 8 - 1)) {
- cfofBits = cfofBits | (ext & (CFBit | OFBit));
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit | (ext & ECFBit);
} else {
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
}
'''
@@ -579,11 +582,11 @@ let {{
'''
flag_code = '''
if (ProdHi) {
- cfofBits = cfofBits | (ext & (CFBit | OFBit));
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit | (ext & ECFBit);
} else {
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
}
'''
@@ -682,9 +685,9 @@ let {{
big_code = divCode % "DestReg = remaining & mask(dataSize * 8);"
flag_code = '''
if (remaining == 0)
- ezfBit = ezfBit | (ext & EZFBit);
+ PredezfBit = PredezfBit | (ext & EZFBit);
else
- ezfBit = ezfBit & ~(ext & EZFBit);
+ PredezfBit = PredezfBit & ~(ext & EZFBit);
'''
class Divq(RdRegOp):
@@ -715,8 +718,8 @@ let {{
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
int CFBits = 0;
//Figure out if we -would- set the CF bits if requested.
@@ -727,20 +730,22 @@ let {{
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && CFBits) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Figure out what the OF bit should be.
if ((ext & OFBit) && (CFBits ^ bits(DestReg, dataSize * 8 - 1)))
- cfofBits = cfofBits | OFBit;
+ PredcfofBits = PredcfofBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -763,27 +768,29 @@ let {{
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) &&
shiftAmt <= dataSize * 8 &&
bits(SrcReg1, shiftAmt - 1)) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Figure out what the OF bit should be.
if ((ext & OFBit) && bits(SrcReg1, dataSize * 8 - 1))
- cfofBits = cfofBits | OFBit;
+ PredcfofBits = PredcfofBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -808,24 +815,26 @@ let {{
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
//If some combination of the CF bits need to be set, set them.
uint8_t effectiveShift =
(shiftAmt <= dataSize * 8) ? shiftAmt : (dataSize * 8);
if ((ext & (CFBit | ECFBit)) &&
bits(SrcReg1, effectiveShift - 1)) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -846,28 +855,30 @@ let {{
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
//Find the most and second most significant bits of the result.
int msb = bits(DestReg, dataSize * 8 - 1);
int smsb = bits(DestReg, dataSize * 8 - 2);
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && msb) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Figure out what the OF bit should be.
if ((ext & OFBit) && (msb ^ smsb))
- cfofBits = cfofBits | OFBit;
+ PredcfofBits = PredcfofBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -892,28 +903,30 @@ let {{
int origCFBit = (cfofBits & CFBit) ? 1 : 0;
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
//Figure out what the OF bit should be.
if ((ext & OFBit) && (origCFBit ^
bits(SrcReg1, dataSize * 8 - 1))) {
- cfofBits = cfofBits | OFBit;
+ PredcfofBits = PredcfofBits | OFBit;
}
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) &&
(realShiftAmt == 0) ? origCFBit :
bits(SrcReg1, realShiftAmt - 1)) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -935,28 +948,30 @@ let {{
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
//The CF bits, if set, would be set to the lsb of the result.
int lsb = DestReg & 0x1;
int msb = bits(DestReg, dataSize * 8 - 1);
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && lsb) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Figure out what the OF bit should be.
if ((ext & OFBit) && (msb ^ lsb))
- cfofBits = cfofBits | OFBit;
+ PredcfofBits = PredcfofBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -983,28 +998,30 @@ let {{
int origCFBit = (cfofBits & CFBit) ? 1 : 0;
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
int msb = bits(DestReg, dataSize * 8 - 1);
int CFBits = bits(SrcReg1, dataSize * 8 - realShiftAmt);
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) &&
(realShiftAmt == 0) ? origCFBit : CFBits) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Figure out what the OF bit should be.
if ((ext & OFBit) && (msb ^ CFBits))
- cfofBits = cfofBits | OFBit;
+ PredcfofBits = PredcfofBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -1032,8 +1049,8 @@ let {{
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
int CFBits = 0;
//Figure out if we -would- set the CF bits if requested.
@@ -1048,21 +1065,23 @@ let {{
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && CFBits) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Figure out what the OF bit should be.
if ((ext & OFBit) && (bits(SrcReg1, dataBits - 1) ^
bits(result, dataBits - 1)))
- cfofBits = cfofBits | OFBit;
+ PredcfofBits = PredcfofBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -1096,8 +1115,8 @@ let {{
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
- cfofBits = cfofBits & ~(ext & (CFBit | OFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit | OFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
int CFBits = 0;
//If some combination of the CF bits need to be set, set them.
@@ -1112,21 +1131,23 @@ let {{
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && CFBits) {
- cfofBits = cfofBits | (ext & CFBit);
- ecfBit = ecfBit | (ext & ECFBit);
+ PredcfofBits = PredcfofBits | (ext & CFBit);
+ PredecfBit = PredecfBit | (ext & ECFBit);
}
//Figure out what the OF bit should be.
if ((ext & OFBit) && (bits(SrcReg1, dataBits - 1) ^
bits(result, dataBits - 1)))
- cfofBits = cfofBits | OFBit;
+ PredcfofBits = PredcfofBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
- uint64_t newFlags = genFlags(ccFlagBits | dfBit | ezfBit,
- ext & ~(CFBit | ECFBit | OFBit), DestReg, psrc1, op2);
- ezfBit = newFlags & EZFBit;
- dfBit = newFlags & DFBit;
- ccFlagBits = newFlags & ccFlagMask;
+ uint64_t newFlags = genFlags(PredccFlagBits | PreddfBit |
+ PredezfBit, ext & ~(CFBit | ECFBit | OFBit),
+ DestReg, psrc1, op2);
+
+ PredezfBit = newFlags & EZFBit;
+ PreddfBit = newFlags & DFBit;
+ PredccFlagBits = newFlags & ccFlagMask;
}
'''
@@ -1244,15 +1265,15 @@ let {{
flag_code = '''
if (!sign_bit) {
- ccFlagBits = ccFlagBits & ~(ext & (ZFBit));
- cfofBits = cfofBits & ~(ext & (CFBit));
- ecfBit = ecfBit & ~(ext & ECFBit);
- ezfBit = ezfBit & ~(ext & EZFBit);
+ PredccFlagBits = PredccFlagBits & ~(ext & (ZFBit));
+ PredcfofBits = PredcfofBits & ~(ext & (CFBit));
+ PredecfBit = PredecfBit & ~(ext & ECFBit);
+ PredezfBit = PredezfBit & ~(ext & EZFBit);
} else {
- ccFlagBits = ccFlagBits | (ext & (ZFBit));
- cfofBits = cfofBits | (ext & (CFBit));
- ecfBit = ecfBit | (ext & ECFBit);
- ezfBit = ezfBit | (ext & EZFBit);
+ PredccFlagBits = PredccFlagBits | (ext & (ZFBit));
+ PredcfofBits = PredcfofBits | (ext & (CFBit));
+ PredecfBit = PredecfBit | (ext & ECFBit);
+ PredezfBit = PredezfBit | (ext & EZFBit);
}
'''
@@ -1535,12 +1556,12 @@ let {{
'''
flag_code = '''
// Check for a NULL selector and set ZF,EZF appropriately.
- ccFlagBits = ccFlagBits & ~(ext & ZFBit);
- ezfBit = ezfBit & ~(ext & EZFBit);
+ PredccFlagBits = PredccFlagBits & ~(ext & ZFBit);
+ PredezfBit = PredezfBit & ~(ext & EZFBit);
if (!selector.si && !selector.ti) {
- ccFlagBits = ccFlagBits | (ext & ZFBit);
- ezfBit = ezfBit | (ext & EZFBit);
+ PredccFlagBits = PredccFlagBits | (ext & ZFBit);
+ PredezfBit = PredezfBit | (ext & EZFBit);
}
'''
diff --git a/src/arch/x86/isa/operands.isa b/src/arch/x86/isa/operands.isa
index e0cd2d628..05b127e37 100644
--- a/src/arch/x86/isa/operands.isa
+++ b/src/arch/x86/isa/operands.isa
@@ -116,13 +116,45 @@ def operands {{
(None, None, 'IsControl'), 50),
'nuIP': ('PCState', 'uqw', 'nupc',
(None, None, 'IsControl'), 50),
- # This holds the condition code portion of the flag register. The
- # nccFlagBits version holds the rest.
+ # These registers hold the condition code portion of the flag
+ # register. The nccFlagBits version holds the rest.
'ccFlagBits': intReg('INTREG_PSEUDO(0)', 60),
'cfofBits': intReg('INTREG_PSEUDO(1)', 61),
'dfBit': intReg('INTREG_PSEUDO(2)', 62),
'ecfBit': intReg('INTREG_PSEUDO(3)', 63),
'ezfBit': intReg('INTREG_PSEUDO(4)', 64),
+
+ # These Pred registers are to be used where reading the portions of
+ # condition code registers is possibly optional, depending on how the
+ # check evaluates. There are two checks being specified, one tests if
+ # a register needs to be read, the other tests whether the register
+ # needs to be written to. It is unlikely that these would need to be
+ # used in the actual operation of the instruction. It is expected
+ # that these are used only in the flag code.
+
+ # Rationale behind the checks: at times, we need to partially update
+ # the condition code bits in a register. So we read the register even
+ # in the case when the all the bits will be written, or none of the
+ # bits will be written. The read predicate checks if any of the bits
+ # would be retained, the write predicate checks if any of the bits
+ # are being written.
+
+ 'PredccFlagBits': ('IntReg', 'uqw', 'INTREG_PSEUDO(0)', 'IsInteger',
+ 60, None, None, '''(((ext & (PFBit | AFBit | ZFBit | SFBit
+ )) != (PFBit | AFBit | ZFBit | SFBit )) &&
+ ((ext & (PFBit | AFBit | ZFBit | SFBit )) != 0))''',
+ '((ext & (PFBit | AFBit | ZFBit | SFBit )) != 0)'),
+ 'PredcfofBits': ('IntReg', 'uqw', 'INTREG_PSEUDO(1)', 'IsInteger',
+ 61, None, None, '''(((ext & CFBit) == 0 ||
+ (ext & OFBit) == 0) && ((ext & (CFBit | OFBit)) != 0))''',
+ '((ext & (CFBit | OFBit)) != 0)'),
+ 'PreddfBit': ('IntReg', 'uqw', 'INTREG_PSEUDO(2)', 'IsInteger',
+ 62, None, None, '(false)', '((ext & DFBit) != 0)'),
+ 'PredecfBit': ('IntReg', 'uqw', 'INTREG_PSEUDO(3)', 'IsInteger',
+ 63, None, None, '(false)', '((ext & ECFBit) != 0)'),
+ 'PredezfBit': ('IntReg', 'uqw', 'INTREG_PSEUDO(4)', 'IsInteger',
+ 64, None, None, '(false)', '((ext & EZFBit) != 0)'),
+
# These register should needs to be more protected so that later
# instructions don't map their indexes with an old value.
'nccFlagBits': controlReg('MISCREG_RFLAGS', 65),