sanchayanmaity/gem5
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

X86: Make the shift and rotate instructions set the carry flag(s) and overflow flags like they're supposed to.

Browse source 
--HG--
extra : convert_revision : c0523a5bbf53375ce979ca7d98a95e465be66fbe
This commit is contained in:
Gabe Black 2007-09-13 16:35:20 -07:00
parent f7b6230d99
commit 534c6a800a
1 changed files with 136 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

143
src/arch/x86/isa/microops/regop.isa
View file

@ -612,13 +612,34 @@ let {{
# Shift instructions
class Sll(FlagRegOp):
class Sll(RegOp):
code = '''
uint8_t shiftAmt = (op2 & ((dataSize == 8) ? mask(6) : mask(5)));
DestReg = merge(DestReg, psrc1 << shiftAmt, dataSize);
'''
flag_code = '''
// If the shift amount is zero, no flags should be modified.
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
ccFlagBits = ccFlagBits & ~(ext & (CFBit | ECFBit | OFBit));
int CFBits = 0;
//Figure out if we -would- set the CF bits if requested.
if (bits(SrcReg1, dataSize * 8 - shiftAmt))
CFBits = 1;
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && CFBits)
ccFlagBits = ccFlagBits | (ext & (CFBit | ECFBit));
//Figure out what the OF bit should be.
if ((ext & OFBit) && (CFBits ^ bits(DestReg, dataSize * 8 - 1)))
ccFlagBits = ccFlagBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
ccFlagBits = genFlags(ccFlagBits, ext & ~(CFBit | ECFBit | OFBit),
DestReg, psrc1, op2);
}
'''
class Srl(FlagRegOp):
class Srl(RegOp):
code = '''
uint8_t shiftAmt = (op2 & ((dataSize == 8) ? mask(6) : mask(5)));
// Because what happens to the bits shift -in- on a right shift
@ -627,8 +648,25 @@ let {{
uint64_t logicalMask = mask(dataSize * 8 - shiftAmt);
DestReg = merge(DestReg, (psrc1 >> shiftAmt) & logicalMask, dataSize);
'''
flag_code = '''
// If the shift amount is zero, no flags should be modified.
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
ccFlagBits = ccFlagBits & ~(ext & (CFBit | ECFBit | OFBit));
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && bits(SrcReg1, shiftAmt - 1))
ccFlagBits = ccFlagBits | (ext & (CFBit | ECFBit));
//Figure out what the OF bit should be.
if ((ext & OFBit) && bits(SrcReg1, dataSize * 8 - 1))
ccFlagBits = ccFlagBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
ccFlagBits = genFlags(ccFlagBits, ext & ~(CFBit | ECFBit | OFBit),
DestReg, psrc1, op2);
}
'''
class Sra(FlagRegOp):
class Sra(RegOp):
code = '''
uint8_t shiftAmt = (op2 & ((dataSize == 8) ? mask(6) : mask(5)));
// Because what happens to the bits shift -in- on a right shift
@ -638,8 +676,22 @@ let {{
-bits(psrc1, dataSize * 8 - 1) << (dataSize * 8 - shiftAmt);
DestReg = merge(DestReg, (psrc1 >> shiftAmt) | arithMask, dataSize);
'''
flag_code = '''
// If the shift amount is zero, no flags should be modified.
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
ccFlagBits = ccFlagBits & ~(ext & (CFBit | ECFBit | OFBit));
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && bits(SrcReg1, shiftAmt - 1))
ccFlagBits = ccFlagBits | (ext & (CFBit | ECFBit));
//Use the regular mechanisms to calculate the other flags.
ccFlagBits = genFlags(ccFlagBits, ext & ~(CFBit | ECFBit | OFBit),
DestReg, psrc1, op2);
}
'''
class Ror(FlagRegOp):
class Ror(RegOp):
code = '''
uint8_t shiftAmt =
(op2 & ((dataSize == 8) ? mask(6) : mask(5)));
@ -652,8 +704,28 @@ let {{
else
DestReg = DestReg;
'''
flag_code = '''
// If the shift amount is zero, no flags should be modified.
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
ccFlagBits = ccFlagBits & ~(ext & (CFBit | ECFBit | OFBit));
//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)
ccFlagBits = ccFlagBits | (ext & (CFBit | ECFBit));
//Figure out what the OF bit should be.
if ((ext & OFBit) && (msb ^ smsb))
ccFlagBits = ccFlagBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
ccFlagBits = genFlags(ccFlagBits, ext & ~(CFBit | ECFBit | OFBit),
DestReg, psrc1, op2);
}
'''
class Rcr(FlagRegOp):
class Rcr(RegOp):
code = '''
uint8_t shiftAmt =
(op2 & ((dataSize == 8) ? mask(6) : mask(5)));
@ -669,8 +741,26 @@ let {{
else
DestReg = DestReg;
'''
flag_code = '''
// If the shift amount is zero, no flags should be modified.
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
ccFlagBits = ccFlagBits & ~(ext & (CFBit | ECFBit | OFBit));
//Figure out what the OF bit should be.
if ((ext & OFBit) && ((ccFlagBits & CFBit) ^
bits(SrcReg1, dataSize * 8 - 1)))
ccFlagBits = ccFlagBits | OFBit;
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && bits(SrcReg1, shiftAmt - 1))
ccFlagBits = ccFlagBits | (ext & (CFBit | ECFBit));
//Use the regular mechanisms to calculate the other flags.
ccFlagBits = genFlags(ccFlagBits, ext & ~(CFBit | ECFBit | OFBit),
DestReg, psrc1, op2);
}
'''
class Rol(FlagRegOp):
class Rol(RegOp):
code = '''
uint8_t shiftAmt =
(op2 & ((dataSize == 8) ? mask(6) : mask(5)));
@ -684,8 +774,28 @@ let {{
else
DestReg = DestReg;
'''
flag_code = '''
// If the shift amount is zero, no flags should be modified.
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
ccFlagBits = ccFlagBits & ~(ext & (CFBit | ECFBit | OFBit));
//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)
ccFlagBits = ccFlagBits | (ext & (CFBit | ECFBit));
//Figure out what the OF bit should be.
if ((ext & OFBit) && (msb ^ lsb))
ccFlagBits = ccFlagBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
ccFlagBits = genFlags(ccFlagBits, ext & ~(CFBit | ECFBit | OFBit),
DestReg, psrc1, op2);
}
'''
class Rcl(FlagRegOp):
class Rcl(RegOp):
code = '''
uint8_t shiftAmt =
(op2 & ((dataSize == 8) ? mask(6) : mask(5)));
@ -703,6 +813,25 @@ let {{
else
DestReg = DestReg;
'''
flag_code = '''
// If the shift amount is zero, no flags should be modified.
if (shiftAmt) {
//Zero out any flags we might modify. This way we only have to
//worry about setting them.
ccFlagBits = ccFlagBits & ~(ext & (CFBit | ECFBit | OFBit));
int msb = bits(DestReg, dataSize * 8 - 1);
int CFBits = bits(SrcReg1, dataSize * 8 - shiftAmt);
//If some combination of the CF bits need to be set, set them.
if ((ext & (CFBit | ECFBit)) && CFBits)
ccFlagBits = ccFlagBits | (ext & (CFBit | ECFBit));
//Figure out what the OF bit should be.
if ((ext & OFBit) && (msb ^ CFBits))
ccFlagBits = ccFlagBits | OFBit;
//Use the regular mechanisms to calculate the other flags.
ccFlagBits = genFlags(ccFlagBits, ext & ~(CFBit | ECFBit | OFBit),
DestReg, psrc1, op2);
}
'''
class Wrip(WrRegOp, CondRegOp):
code = 'RIP = psrc1 + op2'