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authorGabe Black <gblack@eecs.umich.edu>2007-09-13 16:35:20 -0700
committerGabe Black <gblack@eecs.umich.edu>2007-09-13 16:35:20 -0700
commit534c6a800ade5499bf37a896993ab86488b6654c (patch)
treee655cda40f3258a0e13f3367e638c405974b5792
parentf7b6230d99e102f3a6195687fed0617005a70424 (diff)
downloadgem5-534c6a800ade5499bf37a896993ab86488b6654c.tar.xz
X86: Make the shift and rotate instructions set the carry flag(s) and overflow flags like they're supposed to.
--HG-- extra : convert_revision : c0523a5bbf53375ce979ca7d98a95e465be66fbe
-rw-r--r--src/arch/x86/isa/microops/regop.isa143
1 files changed, 136 insertions, 7 deletions
diff --git a/src/arch/x86/isa/microops/regop.isa b/src/arch/x86/isa/microops/regop.isa
index 371ff63da..98743e603 100644
--- a/src/arch/x86/isa/microops/regop.isa
+++ b/src/arch/x86/isa/microops/regop.isa
@@ -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'