# Estimate ppc code compression with Libre-SOC encoding attempt v1.
+# Copyright 2020 Alexandre Oliva
+
# This script is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# -- remain in 16-bit mode for the next insn
-# -- take the 16 bits that would be the next compressed insn as an
-# extension to the present 16-bit insn, and remain in 16-bit mode for
-# the subsequent 16-bits
+# - a 16-bit immediate insn in compressed mode, that must be followed
+# by another compressed insn
# At (visible) entry points, mode is forced to return to uncompressed
-# mode.
+# mode. Every branch target must be in uncompressed mode as well, but
+# this script does not enforce that.
# The entire code stream is printed, without any attempt to modify the
# addresses that go along with or in them; we only insert markers for
insn = re.compile('\s+(?P<addr>[0-9a-f]+):\s+(?P<opcode>[^ ]+) *(?P<operands>.*)')
-opkind = re.compile('(?P<reg>(?P<regkind>[cf]?r)(?P<regnum>[0-9]+))|(?P<immediate>-?[0-9]+)|(?P<branch>[0-9a-f]+)(?: <.*>)?|(?P<offset>-?[0-9]+)\((?P<basereg>r[0-9]+)\)')
+# reg is a regkind (r, cr, fr) followed by a regnum
+xreg = '(?P<reg>(?P<regkind>[cf]?r)(?P<regnum>[0-9]+))'
+
+# immediate is a sequence of digits, possibly preceded by a negative sign
+ximm = '(?P<immediate>-?[0-9]+)'
+
+# branch is a branch target address; ignore an angle-bracketed label after it
+xbrt = '(?P<branch>[0-9a-f]+)(?: <.*>)?'
+
+# offset is like immediate, but followed by a parenthesized basereg
+xoff = '(?P<offset>-?[0-9]+)\((?P<basereg>r[0-9]+)\)'
+# creg is the cr, cond names one of its bits
+crbit = '(?:4\*(?P<creg>cr[0-7])\+)?(?P<cond>gt|lt|eq|so)'
+
+# Combine the above into alternatives, to easily classify operands by
+# pattern matching.
+opkind = re.compile('|'.join([xreg, ximm, xbrt, xoff, crbit]))
+
+# Pre-parse and classify op into a mop, short for mapped op.
def mapop(op):
match = opkind.fullmatch(op)
- int (addr, 16)).bit_length (), op, addr)
elif match['offset'] is not None:
op = ('ofst', mapop(match['offset']), mapop(match['basereg']), op)
+ elif match['cond'] is not None:
+ if match['creg'] is None:
+ creg = 'cr0'
+ else:
+ creg = match['creg']
+ op = ('crbit', mapop(creg), ('cond', match['cond']), op)
else:
raise "unrecognized operand kind"
return op
+# Accessor to enable the mapop representation to change easily.
def opclass(mop):
return mop[0]
+
+# Some opclass predicates, for the same reason.
+def regp(mop):
+ return opclass(mop) in { 'r', 'fr', 'cr' } \
+ or (opclass(mop) is 'imm' and mop[1] is 0)
+def immp(mop):
+ return opclass(mop) in { 'imm', 'pcoff' }
+def rofp(mop):
+ return opclass(mop) is 'ofst'
+def crbt(mop):
+ return opclass(mop) is 'crbit'
+
+# Some more accessors.
+
+# Return the reg number if mop fits regp.
def regno(mop):
- if mop[0] in { 'r', 'fr', 'cr' }:
+ if regp(mop) \
+ or (immp(mop) and mop[1] is 0):
return mop[1]
- else:
- raise "operand is not a register"
+ raise "operand is not a register"
+def immval(mop):
+ if immp(mop):
+ return int(mop[2])
+ raise "operand is not an immediate"
+
+# Return the immediate length if mop fits immp.
def immbits(mop):
- if mop[0] is 'imm':
+ if immp(mop):
return mop[1]
- else:
- raise "operand is not an immediate"
+ raise "operand is not an immediate"
-# Following are predicates to be used in copcond, to tell the mode in
-# which opcode with ops as operands is to be represented
+# Return the register sub-mop if mop fits rofp.
+def rofreg(mop):
+ if rofp(mop):
+ return mop[2]
+ raise "operand is not an offset"
-# Any occurrence of the opcode can be compressed.
-def anyops(opcode, ops):
- return 1
+# Return the offset sub-opt if mop fits rofp.
+def rofset(mop):
+ if rofp(mop):
+ return mop[1]
+ raise "operand is not an offset"
-# Compress iff first and second operands are the same.
-def same01(opcode, ops):
- if ops[0] == ops[1]:
- return 1
- else:
- return 0
+# Return the register sub-mop if mop fits crbit.
+def crbtreg(mop):
+ if crbt(mop):
+ return mop[1]
+ raise "operand is not a condition register bit"
+
+# Return the cond bit name if mop fits crbit.
+def crbtcnd(mop):
+ if crbt(mop):
+ return mop[2]
+ raise "operand is not a condition register bit"
+
+# Following are predicates to be used in copcond, to tell the mode in
+# which opcode with ops as operands is to be represented.
-# Registers representable in a made-up 3-bit mapping.
# TODO: use insn_histogram.py to show the best targets
# (remember to exclude nop - ori r0,r0,0 as this skews numbers)
-cregs2 = { 1, 2, 3, 4, 5, 6, 7, 31 }
+# Registers representable in a made-up 3-bit mapping.
+# It must contain 0 for proper working of at least storex.
+#cregs3 = { 0, 31, 1, 2, 3, 4, 5, 6, 7 }
+cregs3 = { 0, 9, 3, 1, 2, 31, 10, 30, 4 }
+# Ditto in a 2-bit mapping. It needs not contain 0, but it must be a
+# subset of cregs3 for proper working of at least storex.
+cregs2 = { 9, 3, 1, 2 }
+# Use the same sets for FP for now.
+cfregs3 = cregs3
+cfregs2 = cregs2
+ccregs2 = { 0, 1, 2, 3 }
# Return true iff mop is a regular register present in cregs2
-def bin2regs3(mop):
- return opclass(mop) is 'r' and regno(mop) in cregs2
+def rcregs2(mop):
+ return opclass(mop) in { 'r', 'imm' } and regno(mop) in cregs2
+
+# Return true iff mop is a regular register present in cregs3
+def rcregs3(mop):
+ return opclass(mop) in { 'r', 'imm' } and regno(mop) in cregs3
+
+# Return true iff mop is a floating-point register present in cfregs2
+def rcfregs2(mop):
+ return opclass(mop) is 'fr' and regno(mop) in cfregs2
+
+# Return true iff mop is a floating-point register present in cfregs3
+def rcfregs3(mop):
+ return opclass(mop) is 'fr' and regno(mop) in cfregs3
+
+# Return true iff mop is a condition register present in ccregs2
+def rccregs2(mop):
+ return opclass(mop) is 'cr' and regno(mop) in ccregs2
# Return true iff mop is an immediate of at most 8 bits.
def imm8(mop):
- return opclass(mop) is 'imm' and immbits(mop) <= 8
+ return immp(mop) and immbits(mop) <= 8
+
+# Return true iff mop is an immediate of at most 12 bits.
+def imm12(mop):
+ return immp(mop) and immbits(mop) <= 12
# Compress binary opcodes iff the first two operands (output and first
# input operand) are registers representable in 3 bits in compressed
# mode, and the immediate operand can be represented in 8 bits.
def bin2regs3imm8(opcode, ops):
- if bin2regs3(ops[0]) and bin2regs3(ops[1]) and imm8(ops[2]):
+ if rcregs3(ops[0]) and rcregs3(ops[1]) and imm8(ops[2]):
return 1
- else:
- return 0
+ return 0
+
+# Recognize do-nothing insns, particularly ori r0,r0,0.
+def maybenop(opcode, ops):
+ if opcode in ['ori', 'addi'] and regno(ops[0]) is regno(ops[1]) \
+ and opclass(ops[0]) is 'r' and regno(ops[0]) is 0 \
+ and imm8(ops[2]) and immbits(ops[2]) is 0:
+ return 3
+ return 0
+
+# Recognize an unconditional branch, that can be represented with a
+# 6-bit operand in 10-bit mode, an an additional 4 bits in 16-bit
+# mode. In both cases, the offset is shifted left by 2 bits.
+def uncondbranch(opcode, ops):
+ if imm8(ops[0]):
+ return 3
+ if imm12(ops[0]):
+ return 1
+ return 0
+
+# 2 bits for RT and RA. RB is r0 in 10-bit, and 3 bits in 16-bit ???
+# there's a general assumption that, if an insn can be represented in
+# 10-bits, then it can also be represented in 16 bits. This will not
+# be the case if cregs3 can't represent register 0. For
+# register+offset addresses, we support 16-imm stdi, fstdi, with 3-bit
+# immediates left-shifted by 3; stwi, fstsi, with 2-bit immediates
+# left-shifted by 2; stdspi for 6-bit immediate left-shifted by 3
+# biased by -256, and stwspi for 6-bit immediate left-shifted by 2
+# also biased by -256. fstdi and fstsi store in memory a
+# floating-point register, the others do a general-purpose register.
+def storexaddr(opcode, ops):
+ # Canonicalize offset in ops[1] to reg, imm
+ if rofp(ops[1]):
+ ops = (ops[0], rofreg(ops[1]), rofset(ops[1]))
+ shift = memshifts[opcode[-1]]
+ if immval(ops[2]) & ((1 << shift) - 1) is not 0:
+ return 0
+ if rcregs3(ops[1]) and immbits(ops[2]) <= shift + 3:
+ return 2
+ if regno(ops[1]) is 1 and opclass(ops[0]) is not 'fr' \
+ and (immval(ops[2]) - 256).bit_length() <= shift + 6:
+ return 2
+ # Require offset 0 for compression of non-indexed form.
+ if not regp(ops[2]):
+ return 0
+ # If any of the registers is zero, and the other fits in cregs2,
+ # it fits in 10-bit.
+ if (rcregs2(ops[1]) and regno(ops[2]) is 0) \
+ or (regno(ops[1]) is 0 and rcregs2(ops[2])):
+ return 3
+ # For 16-bit one must fit rcregs2 and the other rcregs3.
+ if (rcregs2(ops[1]) and rcregs3(ops[2])) \
+ or (rcregs3(ops[1]) and rcregs2(ops[2])):
+ return 1
+ return 0
+def rstorex(opcode, ops):
+ if rcregs2(ops[0]):
+ return storexaddr(opcode, ops)
+ return 0
+def frstorex(opcode, ops):
+ if rcfregs2(ops[0]):
+ return storexaddr(opcode, ops)
+ return 0
+
+memshifts = { 'd': 3, 'w': 2, 'z': 2, 's': 2 }
+
+# 3 bits for RA, 3 bits for RB, 3 bits for RT for 16-bit. for 10-bit,
+# RB and RT must match. ??? It's not clear what that means WRT
+# register mapping of different kinds of registers, e.g. when RT is a
+# floating-point register..
+# For register+offset addresses, we support 16-imm ldi, fldi, with
+# 3-bit immediates left-shifted by 3; lwi, flsi, with 2-bit immediates
+# left-shifted by 2; ldspi for 6-bit immediate left-shifted by 3
+# biased by -256, and lwspi for 6-bit immediate left-shifted by 2 also
+# biased by -256. fldi and flsi load to floating-point registers, the
+# others load to general-purpose registers.
+def loadxaddr(opcode, ops):
+ if rofp(ops[1]):
+ ops = (ops[0], rofreg(ops[1]), rofset(ops[1]))
+ shift = memshifts[opcode[-1]]
+ if immval(ops[2]) & ((1 << shift) - 1) is not 0:
+ return 0
+ if rcregs3(ops[1]) and immbits(ops[2]) <= shift + 3:
+ return 2
+ if regno(ops[1]) is 1 and opclass(ops[0]) is not 'fr' \
+ and (immval(ops[2]) - 256).bit_length() <= shift + 6:
+ return 2
+ # Otherwise require offset 0 for compression of non-indexed form.
+ if not regp(ops[2]):
+ return 0
+ if rcregs3(ops[1]) and rcregs3(ops[2]):
+ if regno(ops[0]) in { regno(ops[1]), regno(ops[2]) }:
+ return 3
+ return 1
+ return 0
+def rloadx(opcode, ops):
+ if rcregs3(ops[0]):
+ return loadxaddr(opcode, ops)
+ return 0
+def frloadx(opcode, ops):
+ if rcfregs3(ops[0]):
+ return loadxaddr(opcode, ops)
+ return 0
+
+# 3 bits for RA, 3 bits for RB, 3 bits for RT for 16-bit. for 10-bit,
+# RB and RT must match. RA must not be zero, but in 16-bit mode we
+# can swap RA and RB to make it fit.
+def addop(opcode, ops):
+ if rcregs3(ops[0]) and rcregs3(ops[1]) and rcregs3(ops[2]):
+ if regno(ops[0]) in { regno(ops[1]), regno(ops[2]) }:
+ return 3
+ if regno(ops[1]) is not 0 or regno(ops[2]) is not 0:
+ return 1
+ return 0
+
+# 3 bits for RA, 3 bits for RB, 3 bits for RT for 16-bit. for 10-bit,
+# RA and RT must match. ??? The spec says RB, but the actual opcode
+# is subf., subtract from, and it subtracts RA from RB. 'neg.' would
+# make no sense as described there if we didn't use RA.
+def subfop(opcode, ops):
+ if rcregs3(ops[0]) and rcregs3(ops[1]) and rcregs3(ops[2]):
+ if regno(ops[0]) is regno(ops[1]):
+ return 3
+ return 1
+ return 0
+def negop(opcode, ops):
+ if rcregs3(ops[0]) and rcregs3(ops[1]):
+ return 3
+ return 0
+
+# 3 bits for RA and 3 bits for RB. L (op1) must be 1 for 10-bit.
+# op0 is a cr, must be zero for 10-bit.
+def cmpop(opcode, ops):
+ if rcregs3(ops[2]) and rcregs3(ops[3]):
+ if regno(ops[0]) is 0 and immval(ops[1]) is 1:
+ return 3
+ return 1
+ return 0
+
+# 3 bits for RS, 3 bits for RB, 3 bits for RS, 16-bit only.
+def sldop(opcode, ops):
+ if rcregs3(ops[0]) and rcregs3(ops[1]) and rcregs3(ops[2]):
+ return 1
+ return 0
+# same as sld, except RS must be nonzero.
+def srdop(opcode, ops):
+ if regno(ops[1]) is not 0:
+ return sldop(opcode, ops)
+ return 0
+# same as sld, except RS is given by RA, so they must be the same.
+def sradop(opcode, ops):
+ if regno(ops[0]) is regno(ops[1]):
+ return sldop(opcode, ops)
+ return 0
+
+# binary logical ops: and, nand, or, nor.
+# 3 bits for RA (nonzero), 3 bits for RB, 3 bits for RT in 16-bit mode.
+# RT is implicitly RB in 10-bit mode.
+def binlog1016ops(opcode, ops):
+ if rcregs3(ops[0]) and rcregs3(ops[1]) and rcregs3(ops[2]) \
+ and regno(ops[1]) is not 0:
+ # mr RT, RB AKA or RT, RB, RB takes the 10-bit encoding
+ # of the 16-bit nor; we've already ruled out r0 as RB above.
+ if regno(ops[0]) is regno(ops[2]) and opcode is not 'nor':
+ return 3
+ # or and and, with two identical inputs, stand for mr.
+ # nor and nand, likewise, stand for not, that has its
+ # own unary 10-bit encoding.
+ if regno(ops[1]) is regno(ops[2]):
+ return 3
+ return 1
+ return 0
+# 3 bits for RB, 3 bits for RT in 16-bit mode.
+# RT is implicitly RB in 10-bit mode.
+def unlog1016ops(opcode, ops):
+ if rcregs3(ops[0]) and rcregs3(ops[1]):
+ if regno(ops[0]) is regno(ops[1]):
+ return 3
+ return 1
+ return 0
+# 16-bit only logical ops; no 10-bit encoding available
+# same constraints as the 1016 ones above.
+def binlog16ops(opcode, ops):
+ if rcregs3(ops[0]) and rcregs3(ops[1]) and rcregs3(ops[2]) \
+ and regno(ops[1]) is not 0:
+ return 1
+ return 0
+def unlog16ops(opcode, ops):
+ if rcregs3(ops[0]) and rcregs3(ops[1]):
+ return 1
+ return 0
+
+# binary floating-point ops
+# 3 bits for FRA (nonzero), 3 bits for FRB, 3 bits for FRT in 16-bit mode.
+# FRT is implicitly FRB in 10-bit mode.
+def binfp1016ops(opcode, ops):
+ if rcfregs3(ops[0]) and rcfregs3(ops[1]) and rcfregs3(ops[2]) \
+ and regno(ops[1]) is not 0:
+ if regno(ops[0]) is regno(ops[2]):
+ return 3
+ return 1
+ return 0
+def unfp1016ops(opcode, ops):
+ if rcfregs3(ops[0]) and rcfregs3(ops[1]):
+ if regno(ops[0]) is regno(ops[1]):
+ return 3
+ return 1
+ return 0
+def binfp16ops(opcode, ops):
+ if rcfregs3(ops[0]) and rcfregs3(ops[1]) and rcfregs3(ops[2]) \
+ and regno(ops[1]) is not 0:
+ return 1
+ return 0
+def unfp16ops(opcode, ops):
+ if rcfregs3(ops[0]) and rcfregs3(ops[1]):
+ return 1
+ return 0
+
+def cnvfp16ops(opcode, ops):
+ if rcfregs2(ops[0]) and rcfregs2(ops[1]):
+ return 1
+ return 0
+
+# Move between CRs. 3 bits for destination, 3 bits for source in
+# 16-bit mode. That covers all possibilities. For 10-bit mode, only
+# 2 bits for destination.
+def mcrfop(opcode, ops):
+ if rccregs2(ops[0]):
+ return 3
+ return 1
+# Logical ops between two CRs into one. 2 bits for destination, that
+# must coincide with one of the inputs, 3 bits for the other input.
+# 16-bit only.
+def crops(opcode, ops):
+ if rccregs2(ops[0]) and regno(ops[0]) is regno(ops[1]):
+ return 1
+ return 0
+
+# 3 bits for general-purpose register; immediate identifies the
+# special purpose register to move to: 8 for lr, 9 for ctr. 16-bit
+# only. mtspr imm,rN moves from rN to the spr; mfspr rN,imm moves
+# from spr to rN.
+def mtsprops(opcode, ops):
+ if immval(ops[0]) in (8, 9) and rcregs3(ops[1]):
+ return 1
+ return 0
+def mfsprops(opcode, ops):
+ if immval(ops[1]) in (8, 9) and rcregs3(ops[0]):
+ return 1
+ return 0
+
+# 3 bits for nonzero general-purpose register; the immediate is a
+# per-CR mask (8-bits). mtcr rN is mtcrf 0xFF, rN. mfcr rN is a raw
+# opcode, not an alias.
+def mtcrfops(opcode, ops):
+ if immval(ops[0]) is 255 and rcregs3(ops[1]) and regno(ops[1]) is not 0:
+ return 1
+ return 0
+def mfcrops(opcode, ops):
+ if rcregs3(ops[0]) and regno(ops[0]) is not 0:
+ return 1
+ return 0
+
+# 3 bits for destination and source register, must be the same. Full
+# shift range fits. 16-imm format.
+def shiftops(opcode, ops):
+ if rcregs3(ops[0]) and regno(ops[0]) is regno(ops[1]):
+ return 2
+ return 0
+
+# For 16-imm 'addis' and 'addi', we have 3 bits (nonzero) for the
+# destination register, source register is implied 0, the immediate
+# must either fit in signed 5-bit, left-shifted by 3, or in signed
+# 7-bit without shift. ??? That seems backwards.
+def addiops(opcode, ops):
+ if rcregs3(ops[0]) and regno(ops[0]) is not 0 \
+ and regno(ops[1]) is 0 and imm8(ops[2]) \
+ and immbits(ops[2]) <= 8 \
+ and ((immval(ops[2]) & 7) is 0 or immbits(ops[2]) <= 7):
+ return 2
+ return maybenop(opcode, ops)
+
+# cmpdi and cmpwi are aliases to uncompressed cmp CR#, L, RA, imm16,
+# CR# being the target condition register, L being set for d rather
+# than w. In 16-imm, CR# must be zero, RA must fit in 3 bits, and the
+# immediate must be 6 bits signed.
+def cmpiops(opcode, ops):
+ if regno(ops[0]) is 0 and immval(ops[1]) in (0,1) \
+ and rcregs3(ops[2]) and immbits(ops[3]) <= 6:
+ return 2
+ return 0
+
+# 16-imm bc, with or without LK, uses 3 bits for BI (CR0 and CR1 only),
+# and 1 bit for BO1 (to tell BO 12 from negated 4).
+def bcops(opcode, ops):
+ if immval(ops[0]) in (4,12) and regno(crbtreg(ops[1])) <= 1 \
+ and immbits(ops[2]) <= 8:
+ return 2
+ return 0
+
+# 2 bits for BI and 3 bits for BO in 10-bit encoding; one extra bit
+# for each in 16-bit.
+def bclrops(opcode, ops):
+ if immval(ops[0]) <= 15 and regno(crbtreg(ops[1])) <= 1 \
+ and immbits(ops[2]) is 0:
+ if immval(ops[0]) <= 7 and regno(crbtreg(ops[1])) is 0:
+ return 3
+ return 1
+ return 0
# Map opcodes that might be compressed to a function that returns the
# best potential encoding kind for the insn, per the numeric coding
# below.
copcond = {
-
+ 'ori': maybenop,
+ # 'attn': binutils won't ever print this
+ 'b': uncondbranch, 'bl': uncondbranch,
+ 'bc': bcops, 'bcl': bcops,
+ 'bclr': bclrops, 'bclrl': bclrops,
+ # Stores and loads, including 16-imm ones
+ 'stdx': rstorex, 'stwx': rstorex,
+ 'std': rstorex, 'stw': rstorex, # only offset zero
+ 'stfdx': frstorex, 'stfsx': frstorex,
+ 'stfd': frstorex, 'stfs': frstorex, # only offset zero
+ # Assuming lwz* rather than lwa*.
+ 'ldx': rloadx, 'lwzx': rloadx,
+ 'ld': rloadx, 'lwz': rloadx, # only offset zero
+ 'lfdx': rloadx, 'lfsx': rloadx,
+ 'lfd': rloadx, 'lfs': rloadx, # only offset zero
+ 'add': addop,
+ 'subf.': subfop, 'neg.': negop,
+ # Assuming cmpl stands for cmpd, i.e., cmp with L=1.
+ # cmpw is cmp with L=0, 16-bit only.
+ 'cmp': cmpop,
+ 'sld.': sldop, 'srd.': srdop, 'srad.': sradop,
+ 'and': binlog1016ops, 'nand': binlog1016ops,
+ 'or': binlog1016ops, 'nor': binlog1016ops,
+ # assuming popcnt and cntlz mean the *d opcodes.
+ 'popcntd': unlog1016ops, 'cntlzd': unlog1016ops, 'extsw': unlog1016ops,
+ # not RT, RB is mapped to nand/nor RT, RB, RB.
+ 'xor': binlog16ops, 'eqv': binlog16ops,
+ # 'setvl.': unlog16ops, # ??? What's 'setvl.'?
+ # assuming cnttz mean the *d opcode.
+ 'cnttzd': unlog16ops, 'extsb': unlog16ops, 'extsh': unlog16ops,
+ 'fsub.': binfp1016ops, 'fadd': binfp1016ops, 'fmul': binfp1016ops,
+ 'fneg.': unfp1016ops,
+ 'fdiv': binfp16ops,
+ 'fabs.': unfp16ops, 'fmr.': unfp16ops,
+ # ??? are these the intended fp2int and int2fp, for all
+ # combinations of signed/unsigned float/double?
+ 'fcfid': cnvfp16ops, 'fctidz': cnvfp16ops,
+ 'fcfidu': cnvfp16ops, 'fctiduz': cnvfp16ops,
+ 'fcfids': cnvfp16ops, 'fctiwz': cnvfp16ops,
+ 'fcfidus': cnvfp16ops, 'fctiwuz': cnvfp16ops,
+ # Condition register opcodes.
+ 'mcrf': mcrfop,
+ 'crnor': crops,
+ 'crandc': crops,
+ 'crxor': crops,
+ 'crnand': crops,
+ 'crand': crops,
+ 'creqv': crops,
+ 'crorc': crops,
+ 'cror': crops,
+ # System opcodes.
+ # 'cbank' is not a ppc opcode, not handled
+ 'mtspr': mtsprops, # raw opcode for 'mtlr', 'mtctr'
+ 'mfspr': mfsprops, # raw opcode for 'mflr', 'mfctr'
+ 'mtcrf': mtcrfops, # raw opcode for 'mtcr'
+ 'mfcr': mfcrops,
+ # 16-imm opcodes.
+ 'sradi.': shiftops, 'srawi.': shiftops,
+ 'addi': addiops,
+ 'cmpi': cmpiops, # raw opcode for 'cmpwi', 'cmpdi'
+ # 'setvli', 'setmvli' are not ppc opcodes, not handled.
}
# We have 4 kinds of insns:
# 0: uncompressed; leave input insn unchanged
# 1: 16-bit compressed, only in compressed mode
-# 2: 16-bit extended by another 16-bit, only in compressed mode
+# 2: 16-imm, i.e., compressed insn that can't switch-out of compressed mode
# 3: 10-bit compressed, may switch to compressed mode
# count[0:3] count the occurrences of the base kinds.
# count[4] counts extra 10-bit nop-switches to compressed mode,
-# tentatively introduced before insns that can be 16-bit encoded.
-count = [0,0,0,0,0]
-# Default comments for the insn kinds above. 2 is always tentative.
-comments = ['', '\t; 16-bit', '\t; tentative 16+16-bit', '\t; 10-bit']
-
-# cur stands for the insn kind that we read and processed in the
-# previous iteration of the loop, and prev is the one before it. the
+# tentatively introduced before insns that can be 16-bit encoded.
+# count[5] counts extra 10-bit nop-switches to compressed mode,
+# tentatively introduced before insns that can be 16-imm encoded.
+# count[6] counts extra 16-bit nop-switches back to uncompressed,
+# introduced after a 16-imm insn.
+# count[7] counts pairs of 10-bit nop-switches and 16-imm insns
+# that turned out to be followed by 32-bit insns. We assume
+# a compressor would backtrack the pair into as a single 32-bit
+# insn, so as to avoid a switch-back nop. The nop and 16-imm
+# insns remain counted as such, so we count these occurrences
+# here.
+count = [0,0,0,0,0,0,0,0]
+# Default comments for the insn kinds above.
+comments = ['', '\t; 16-bit', '\t; 16-imm', '\t; 10-bit']
+
+# curi stands for the insn kind that we read and processed in the
+# previous iteration of the loop, and previ is the one before it. the
# one we're processing in the current iteration will be stored in
-# nexti until we make it cur at the very end of the loop.
-prev = cur = 0
+# nexti until we make it curi at the very end of the loop.
+previ = curi = 0
for line in sys.stdin:
if line[-1] is '\n':
if match is None:
print(line)
# Switch to uncompressed mode at function boundaries
- prev = prev2 = 0
+ previ = curi = 0
continue
addr = match['addr']
comment = None
- if cur is 0:
+ if curi is 0:
if nexti is 0:
True # Uncompressed mode for good.
elif nexti is 1:
- # If cur was not a single uncompressed mode insn,
+ # If curi was not a single uncompressed mode insn,
# tentatively encode a 10-bit nop to enter compressed
# mode, and then 16-bit. It takes as much space as
# encoding as 32-bit, but offers more possibilities for
# subsequent compressed encodings. A compressor proper
# would have to go back and change the encoding
# afterwards, but wé re just counting.
- if prev is not 1:
- print('\t\th.nop\t\t; tentatively switch to compressed mode')
+ if previ is not 1:
+ print('\t\th.nop\t\t; 10-bit (tentative)')
count[4] += 1
- comment = 'tentatively compressed to 16-bit'
+ comment = '16-bit (tentative)'
+ else:
+ comment = '16-bit auto-back'
elif nexti is 2:
- # We can use compressed encoding for nexti after an
- # uncompressed insn only if it's the single-insn
- # uncompressed mode slot. For anything else, we're better
- # off using uncompressed encoding for nexti, since it makes
- # no sense to spend a 10-bit nop to switch to compressed
- # mode for a 16+16-bit insn. If subsequent insns would
- # benefit from compressed encoding, we can switch then.
- if prev is not 1:
- nexti = 0
- comment = 'not worth a nop for 16+16-bit'
+ # We can use compressed encoding for the 16-imm nexti
+ # after an uncompressed insn without penalty if it's the
+ # single-insn uncompressed mode slot. For other
+ # configurations, we can either remain in uncompressed
+ # mode, or switch to compressed mode with a 10-bit nop.
+ if previ is not 1:
+ print('\t\th.nop\t\t; 10-bit (tentative)')
+ count[5] += 1
+ comment = '16-imm (tentative), vs uncompressed'
+ else:
+ comment = '16-imm auto-back'
elif nexti is 3:
- # If prev was 16-bit compressed, cur would be in the
+ # If previ was 16-bit compressed, curi would be in the
# single-insn uncompressed slot, so nexti could be encoded
# as 16-bit, enabling another 1-insn uncompressed slot
# after nexti that a 10-bit insn wouldn't, so make it so.
- if prev is 1:
+ if previ is 1:
nexti = 1
- comment = '16-bit, could be 10-bit'
- elif cur is 1:
+ comment = '16-bit auto-back, vs 10-bit'
+ elif curi is 1:
# After a 16-bit insn, anything goes. If it remains in 16-bit
# mode, we can have 1 or 2 as nexti; if it returns to 32-bit
# mode, we can have 0 or 3. Using 1 instead of 3 makes room
# that.
if nexti is 3:
nexti = 1
- comment = '16-bit, could be 10-bit'
- elif cur is 2:
- # After a 16+16-bit insn, we can't switch directly to 32-bit
- # mode. However, cur could have been encoded as 32-bit, since
- # any 16+16-bit insn can. Indeed, we may have an arbitrary
- # long sequence of 16+16-bit insns before nexti, and if nexti
- # can only be encoded in 32-bit mode, we can "resolve" all
- # previous adjacent 16+16-bit insns to the corresponding
- # 32-bit insns in the encoding, and "adjust" the 16-bit or
- # 10-bit insn that enabled the potential 16+16-bit encoding to
- # switch to 32-bit mode then instead.
+ comment = '16-bit, vs 10-bit'
+ elif curi is 2:
+ # After a 16-imm insn, we can only switch back to uncompressed
+ # mode with a 16-bit nop.
if nexti is 0:
- prev = cur = 0
- comment = '32-bit, like tentative 16+16-bit insns above'
- elif cur is 3:
+ if previ is 0:
+ print('\t\t\t\t; backtracking pair above to 32-bit')
+ count[7] += 1
+ curi = 0
+ else:
+ print('\t\tc.nop\t\t; forced switch back to uncompressed mode')
+ count[6] += 1
+ previ = curi
+ curi = 1
+ elif nexti is 3:
+ nexti = 1
+ elif curi is 3:
# After a 10-bit insn, another insn that could be encoded as
# 10-bit might as well be encoded as 16-bit, to make room for
# a single-insn uncompressed insn afterwards.
if nexti is 3:
nexti = 1
- comment = '16-bit, could be 10-bit'
+ comment = '16-bit, vs 10-bit'
else:
- raise "unknown mode for previous insn"
+ raise "unknown mode for previious insn"
count[nexti] += 1
print(line + comment)
- prev = cur
- cur = nexti
+ previ = curi
+ curi = nexti
-transition_bytes = 2 * count[4]
-compressed_bytes = 2 * (count[1] + count[3])
-uncompressed_bytes = 4 * (count[0] + count[2])
+transition_bytes = 2 * (count[4] + count[5] + count[6])
+compressed_bytes = 2 * (count[1] + count[2] + count[3])
+uncompressed_bytes = 4 * count[0]
total_bytes = transition_bytes + compressed_bytes + uncompressed_bytes
original_bytes = 2 * compressed_bytes + uncompressed_bytes
print('Summary')
print('32-bit uncompressed instructions: %i' % count[0])
print('16-bit compressed instructions: %i' % count[1])
-print('16+16-bit (tentative) compressed-mode instructions: %i' % count[2])
+print('16-imm compressed-mode instructions: %i' % count[2])
print('10-bit compressed instructions: %i' % count[3])
-print('10-bit (tentative) mode-switching nops: %i' % count[4])
+print('10-bit mode-switching nops: %i' % count[4])
+print('10-bit mode-switching nops for imm-16: %i' % count[5])
+print('16-bit mode-switching nops after imm-16: %i' % count[6])
+print('10-bit nop+16-imm pairs above, backtracked to 32-bit: %i' % count[7])
print('Compressed size estimate: %i' % total_bytes)
print('Original size: %i' % original_bytes)
print('Compressed/original ratio: %f' % (total_bytes / original_bytes))
projects / libreriscv.git / blobdiff