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Comment GetTop a bit better, and also comment out unnecessary logic.

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This commit is contained in:
Jonathan Woodruff
2020-03-05 18:28:45 +00:00
parent 22434499e5
commit 7a50514e7e
1 changed files with 8 additions and 2 deletions
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10
CHERICC_Fat.bsv
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@@ -292,10 +292,16 @@ function LCapAddress getTopFat(CapFat cap, TempFields tf);
Bit#(2) topTip = ret[msbp+1:msbp]; Bit#(2) topTip = ret[msbp+1:msbp];
// Calculate the msb of the base. // Calculate the msb of the base.
CapAddress adr = truncate(cap.address); CapAddress adr = truncate(cap.address);
// First assume that only the address and correction are involved...
Bit#(TSub#(SizeOf#(CapAddress),MW)) bot = truncateLSB(adr) + (signExtend(pack(tf.baseCorrection)) << cap.bounds.exp); Bit#(TSub#(SizeOf#(CapAddress),MW)) bot = truncateLSB(adr) + (signExtend(pack(tf.baseCorrection)) << cap.bounds.exp);
Bit#(1) botTip = msb(bot); Bit#(1) botTip = msb(bot);
if (cap.bounds.exp == (resetExp - 1)) botTip = cap.bounds.baseBits[valueOf(MW)-2]; // If the bit we're interested in are actually coming from baseBits, select the correct one from there.
else if (cap.bounds.exp == (resetExp - 2)) botTip = cap.bounds.baseBits[valueOf(MW)-1]; // exp == (resetExp - 1) doesn't matter since we will not flip unless exp < resetExp-1.
if (cap.bounds.exp == (resetExp - 2)) botTip = cap.bounds.baseBits[valueOf(MW)-1];
// Do the final check.
// If exp >= resetExp - 1, the bits we're looking at are coming directly from topBits and baseBits, are not being inferred,
// and therefore do not need correction. If we are below this range, check that the difference between the resulting top and
// bottom is less than one address space. If not, flip the msb of the top.
if (cap.bounds.exp<(resetExp-1) && (topTip - zeroExtend(botTip)) > 1) ret[msbp+1] = ~ret[msbp+1]; if (cap.bounds.exp<(resetExp-1) && (topTip - zeroExtend(botTip)) > 1) ret[msbp+1] = ~ret[msbp+1];
return ret; return ret;
endfunction endfunction