diff options
author | Kevin Lim <ktlim@umich.edu> | 2005-03-10 15:53:27 -0500 |
---|---|---|
committer | Kevin Lim <ktlim@umich.edu> | 2005-03-10 15:53:27 -0500 |
commit | c12a665c3120b61ed4e09da5d8a52c57406763d5 (patch) | |
tree | b5176be0d526ea24cafcd6f615058651f2b34dfb /cpu/beta_cpu/btb.cc | |
parent | aa8c9db159422a313f6dfc9a76fd827515b32126 (diff) | |
parent | 51108a8c0a3a42702f49a945f8a4dac776a8d189 (diff) | |
download | gem5-c12a665c3120b61ed4e09da5d8a52c57406763d5.tar.xz |
Merge ktlim@zizzer.eecs.umich.edu:/bk/m5
into zamp.eecs.umich.edu:/z/ktlim2/m5
--HG--
extra : convert_revision : a58535776cf5a3d17f8d9f65144cdf8db54289aa
Diffstat (limited to 'cpu/beta_cpu/btb.cc')
-rw-r--r-- | cpu/beta_cpu/btb.cc | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/cpu/beta_cpu/btb.cc b/cpu/beta_cpu/btb.cc new file mode 100644 index 000000000..bceaa66d1 --- /dev/null +++ b/cpu/beta_cpu/btb.cc @@ -0,0 +1,91 @@ +#include <math.h> + +#include "cpu/beta_cpu/btb.hh" +#include "base/trace.hh" + +DefaultBTB::DefaultBTB(unsigned _numEntries, + unsigned _tagBits, + unsigned _instShiftAmt) + : numEntries(_numEntries), + tagBits(_tagBits), + instShiftAmt(_instShiftAmt) +{ + // @todo Check to make sure num_entries is valid (a power of 2) + + DPRINTF(Fetch, "BTB: Creating BTB object.\n"); + + btb = new BTBEntry[numEntries]; + + for (int i = 0; i < numEntries; ++i) + { + btb[i].valid = false; + } + + idxMask = numEntries - 1; + + tagMask = (1 << tagBits) - 1; + + tagShiftAmt = instShiftAmt + (int)log2(numEntries); +} + +inline +unsigned +DefaultBTB::getIndex(const Addr &inst_PC) +{ + // Need to shift PC over by the word offset. + return (inst_PC >> instShiftAmt) & idxMask; +} + +inline +Addr +DefaultBTB::getTag(const Addr &inst_PC) +{ + return (inst_PC >> tagShiftAmt) & tagMask; +} + +bool +DefaultBTB::valid(const Addr &inst_PC) +{ + unsigned btb_idx = getIndex(inst_PC); + + Addr inst_tag = getTag(inst_PC); + + assert(btb_idx < numEntries); + + if (btb[btb_idx].valid && inst_tag == btb[btb_idx].tag) { + return true; + } else { + return false; + } +} + +// @todo Create some sort of return struct that has both whether or not the +// address is valid, and also the address. For now will just use addr = 0 to +// represent invalid entry. +Addr +DefaultBTB::lookup(const Addr &inst_PC) +{ + unsigned btb_idx = getIndex(inst_PC); + + Addr inst_tag = getTag(inst_PC); + + assert(btb_idx < numEntries); + + if (btb[btb_idx].valid && inst_tag == btb[btb_idx].tag) { + return btb[btb_idx].target; + } else { + return 0; + } +} + +void +DefaultBTB::update(const Addr &inst_PC, const Addr &target) +{ + unsigned btb_idx = getIndex(inst_PC); + + assert(btb_idx < numEntries); + + btb[btb_idx].valid = true; + btb[btb_idx].target = target; + btb[btb_idx].tag = getTag(inst_PC); +} |