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arch-arm: RBIT instruction using mirroring func

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The high speed bit-reversing function is now used
for the Aarch64/32 RBIT instruction implementation.

Change-Id: Id5a8a93d928d00fd33ec4061fbb586b8420a1c1b
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5262
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
This commit is contained in:
Giacomo Travaglini
2017-10-18 01:18:46 +01:00
parent 4b3fee0984
commit e79c4c6f03
2 changed files with 2 additions and 23 deletions
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13
src/arch/arm/isa/insts/data64.isa
View File

@@ -248,18 +248,7 @@ let {{
Dest64 = (Op164 == 0) ? intWidth : (intWidth - 1 - findMsbSet(Op164));
''')
buildDataXRegInst("rbit", 1, '''
uint64_t result = Op164;
uint64_t lBit = 1ULL << (intWidth - 1);
uint64_t rBit = 1ULL;
while (lBit > rBit) {
uint64_t maskBits = lBit | rBit;
uint64_t testBits = result & maskBits;
// If these bits are different, swap them by toggling them.
if (testBits && testBits != maskBits)
result ^= maskBits;
lBit >>= 1; rBit <<= 1;
}
Dest64 = result;
Dest64 = reverseBits(Op164, intWidth/8);
''')
buildDataXRegInst("rev", 1, '''
if (intWidth == 32)

12
src/arch/arm/isa/insts/misc.isa
View File

@@ -329,17 +329,7 @@ let {{
exec_output += PredOpExecute.subst(revshIop)
rbitCode = '''
uint8_t *opBytes = (uint8_t *)&Op1;
uint32_t resTemp;
uint8_t *destBytes = (uint8_t *)&resTemp;
// This reverses the bytes and bits of the input, or so says the
// internet.
for (int i = 0; i < 4; i++) {
uint32_t temp = opBytes[i];
temp = (temp * 0x0802 & 0x22110) | (temp * 0x8020 & 0x88440);
destBytes[3 - i] = (temp * 0x10101) >> 16;
}
Dest = resTemp;
Dest = reverseBits(Op1);
'''
rbitIop = InstObjParams("rbit", "Rbit", "RegRegOp",
{ "code": rbitCode,