Pau Cabre has uploaded this change for review. (
https://gem5-review.googlesource.com/c/public/gem5/+/14035
Change subject: cpu: Fixed PC shifting on LTAGE branch predictor
......................................................................
cpu: Fixed PC shifting on LTAGE branch predictor
The PC needs to be shifted according to the instShiftAmt parameter
Change-Id: I272619c093695b56cf7f8ff7163e3b5d23205d16
Signed-off-by: Pau Cabre <pau.ca...@metempsy.com>
---
M src/cpu/pred/ltage.cc
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/src/cpu/pred/ltage.cc b/src/cpu/pred/ltage.cc
index 251fb2e..86b9e99 100644
--- a/src/cpu/pred/ltage.cc
+++ b/src/cpu/pred/ltage.cc
@@ -138,13 +138,14 @@
int
LTAGE::bindex(Addr pc_in) const
{
- return ((pc_in) & ((ULL(1) << (logSizeBiMP)) - 1));
+ return ((pc_in >> instShiftAmt) & ((ULL(1) << (logSizeBiMP)) - 1));
}
int
LTAGE::lindex(Addr pc_in) const
{
- return (((pc_in) & ((ULL(1) << (logSizeLoopPred - 2)) - 1)) << 2);
+ return (((pc_in >> instShiftAmt) &
+ ((ULL(1) << (logSizeLoopPred - 2)) - 1)) << 2);
}
int
@@ -171,7 +172,8 @@
int index;
int hlen = (histLengths[bank] > 16) ? 16 : histLengths[bank];
index =
- (pc) ^ ((pc) >> ((int) abs(tagTableSizes[bank] - bank) + 1)) ^
+ (pc >> instShiftAmt) ^
+ ((pc >> instShiftAmt) >> ((int) abs(tagTableSizes[bank] - bank) +
1)) ^
threadHistory[tid].computeIndices[bank].comp ^
F(threadHistory[tid].pathHist, hlen, bank);
@@ -183,8 +185,9 @@
uint16_t
LTAGE::gtag(ThreadID tid, Addr pc, int bank) const
{
- int tag = (pc) ^ threadHistory[tid].computeTags[0][bank].comp
- ^ (threadHistory[tid].computeTags[1][bank].comp << 1);
+ int tag = (pc >> instShiftAmt) ^
+ threadHistory[tid].computeTags[0][bank].comp ^
+ (threadHistory[tid].computeTags[1][bank].comp << 1);
return (tag & ((ULL(1) << tagWidths[bank]) - 1));
}
@@ -239,7 +242,7 @@
bi->loopHit = -1;
bi->loopPredValid = false;
bi->loopIndex = lindex(pc);
- bi->loopTag = ((pc) >> (logSizeLoopPred - 2));
+ bi->loopTag = ((pc) >> (instShiftAmt + logSizeLoopPred - 2));
for (int i = 0; i < 4; i++) {
if (ltable[bi->loopIndex + i].tag == bi->loopTag) {
@@ -630,7 +633,7 @@
BranchInfo* bi = (BranchInfo*)(b);
ThreadHistory& tHist = threadHistory[tid];
// UPDATE HISTORIES
- bool pathbit = ((branch_pc) & 1);
+ bool pathbit = ((branch_pc >> instShiftAmt) & 1);
//on a squash, return pointers to this and recompute indices.
//update user history
updateGHist(tHist.gHist, taken, tHist.globalHistory, tHist.ptGhist);
--
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Gerrit-Project: public/gem5
Gerrit-Branch: master
Gerrit-Change-Id: I272619c093695b56cf7f8ff7163e3b5d23205d16
Gerrit-Change-Number: 14035
Gerrit-PatchSet: 1
Gerrit-Owner: Pau Cabre <pau.ca...@metempsy.com>
Gerrit-MessageType: newchange
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