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maskgen: support wider granularity result (#665) 

Sometimes it is useful to generate a mask with bits that correspond
to a larger unit than bytes.
This commit is contained in:
Wesley W. Terpstra 2017-04-09 20:06:23 -07:00 committed by GitHub
parent a43bf2feae
commit 71bf929505
1 changed files with 9 additions and 3 deletions
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12
src/main/scala/uncore/tilelink2/package.scala
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@ -33,9 +33,14 @@ package object tilelink2
helper(1, x)
}
// This gets used everywhere, so make the smallest circuit possible ...
def maskGen(addr_lo: UInt, lgSize: UInt, beatBytes: Int): UInt = {
// Given an address and size, create a mask of beatBytes size
// eg: (0x3, 0, 4) => 0001, (0x3, 1, 4) => 0011, (0x3, 2, 4) => 1111
// groupBy applies an interleaved OR reduction; groupBy=2 take 0010 => 01
def maskGen(addr_lo: UInt, lgSize: UInt, beatBytes: Int, groupBy: Int = 1): UInt = {
require (groupBy >= 1 && beatBytes >= groupBy)
require (isPow2(beatBytes) && isPow2(groupBy))
val lgBytes = log2Ceil(beatBytes)
val sizeOH = UIntToOH(lgSize, log2Up(beatBytes))
val sizeOH = UIntToOH(lgSize, log2Up(beatBytes)) | UInt(groupBy*2 - 1)
def helper(i: Int): Seq[(Bool, Bool)] = {
if (i == 0) {
Seq((lgSize >= UInt(lgBytes), Bool(true)))
@ -52,6 +57,7 @@ package object tilelink2
}
}
}
Cat(helper(lgBytes).map(_._1).reverse)
if (groupBy == beatBytes) UInt(1) else
Cat(helper(lgBytes-log2Ceil(groupBy)).map(_._1).reverse)
}
}