riscv/rocket-chip
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Correct FP trap behavior on FCSR

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This commit is contained in:
Andrew Waterman 2013-12-05 04:18:04 -08:00
parent 5814a90472
commit 16d5250924
1 changed files with 21 additions and 16 deletions
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37
rocket/src/main/scala/ctrl.scala
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@ -407,17 +407,22 @@ class Control(implicit conf: RocketConfiguration) extends Module
def checkExceptions(x: Seq[(Bool, UInt)]) =
(x.map(_._1).reduce(_||_), PriorityMux(x))
val fp_csrs = CSRs.fcsr :: CSRs.frm :: CSRs.fflags :: Nil
val legal_csrs = if (conf.fpu) CSRs.all.toSet else CSRs.all.toSet -- fp_csrs
val id_csr_addr = io.dpath.inst(31,20)
val id_csr_en = id_csr != CSR.N
val id_csr_ren = id_raddr1 === UInt(0) && Vec(CSR.S, CSR.C).contains(id_csr)
val id_csr_privileged =
id_csr_addr(9,8) != UInt(0) && id_csr_ren ||
id_csr_addr(11,10) != UInt(0) && id_csr_en
val id_csr_invalid = id_csr_en &&
!Vec(CSRs.all.map(a => UInt(a))).contains(id_csr_addr)
val id_csr_fp = Bool(conf.fpu) && id_csr_en && DecodeLogic(id_csr_addr, fp_csrs, CSRs.all.toSet -- fp_csrs)
val id_csr_wen = id_raddr1 != UInt(0) || !Vec(CSR.S, CSR.C).contains(id_csr)
val id_csr_privileged = id_csr_en &&
(id_csr_addr(9,8) != UInt(0) ||
id_csr_addr(11,10) != UInt(0) && id_csr_wen)
val id_csr_invalid = id_csr_en && !Vec(legal_csrs.map(UInt(_))).contains(id_csr_addr)
// flush pipeline on CSR writes that may have side effects
val id_csr_flush = id_csr_en && !id_csr_ren &&
id_csr_addr != CSRs.sup0 && id_csr_addr != CSRs.sup1 && id_csr_addr != CSRs.epc
val id_csr_flush = {
val safe_csrs = CSRs.sup0 :: CSRs.sup1 :: CSRs.epc :: Nil
id_csr_en && id_csr_wen && DecodeLogic(id_csr_addr, legal_csrs -- safe_csrs, safe_csrs)
}
val id_privileged = id_sret || id_csr_privileged
// stall decode for fences (now, for AMO.aq; later, for AMO.rl and FENCE)
@ -431,14 +436,14 @@ class Control(implicit conf: RocketConfiguration) extends Module
val id_do_fence = id_amo && id_amo_aq || id_fence_i || id_reg_fence && (id_mem_val || id_rocc_val) || id_csr_flush
val (id_xcpt, id_cause) = checkExceptions(List(
(id_interrupt, id_interrupt_cause),
(io.imem.resp.bits.xcpt_ma, UInt(0)),
(io.imem.resp.bits.xcpt_if, UInt(1)),
(!id_int_val.toBool || id_csr_invalid, UInt(2)),
(id_privileged && !io.dpath.status.s, UInt(3)),
(id_fp_val && !io.dpath.status.ef, UInt(4)),
(id_syscall, UInt(6)),
(id_rocc_val && !io.dpath.status.er, UInt(12))))
(id_interrupt, id_interrupt_cause),
(io.imem.resp.bits.xcpt_ma, UInt(0)),
(io.imem.resp.bits.xcpt_if, UInt(1)),
(!id_int_val || id_csr_invalid, UInt(2)),
(id_privileged && !io.dpath.status.s, UInt(3)),
((id_fp_val || id_csr_fp) && !io.dpath.status.ef, UInt(4)),
(id_syscall, UInt(6)),
(id_rocc_val && !io.dpath.status.er, UInt(12))))
ex_reg_xcpt_interrupt := id_interrupt && !take_pc && io.imem.resp.valid
when (id_xcpt) { ex_reg_cause := id_cause }