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/* Current fetch hooks for RISC-V extensions call extensions
* to check PC validity *before* standard fetch processing checks.
*/
function isRVC(h : half) -> bool = ~ (h[1 .. 0] == 0b11)
val fetch : unit -> FetchResult effect {escape, rmem, rreg, wmv, wmvt, wreg}
function fetch() -> FetchResult =
/* fetch PC check for extensions: extensions return a transformed PC to fetch,
* but any exceptions use the untransformed PC.
*/
match ext_fetch_check_pc(PC, PC) {
Ext_FetchAddr_Error(e) => F_Ext_Error(e),
Ext_FetchAddr_OK(use_pc) => {
if (use_pc[0] != bitzero | (use_pc[1] != bitzero & (~ (haveRVC()))))
then F_Error(E_Fetch_Addr_Align, PC)
else match translateAddr(use_pc, Execute) {
TR_Failure(e) => F_Error(e, PC),
TR_Address(ppclo) => {
/* split instruction fetch into 16-bit granules to handle RVC, as
* well as to generate precise fault addresses in any fetch
* exceptions.
*/
match mem_read(Execute, ppclo, 2, false, false, false) {
MemException(e) => F_Error(E_Fetch_Access_Fault, PC),
MemValue(ilo) => {
if isRVC(ilo)
then F_RVC(ilo)
else {
/* fetch PC check for the next instruction granule */
PC_hi : xlenbits = PC + 2;
match ext_fetch_check_pc(PC, PC_hi) {
Ext_FetchAddr_Error(e) => F_Ext_Error(e),
Ext_FetchAddr_OK(use_pc_hi) => {
match translateAddr(use_pc_hi, Execute) {
TR_Failure(e) => F_Error(e, PC_hi),
TR_Address(ppchi) => {
match mem_read(Execute, ppchi, 2, false, false, false) {
MemException(e) => F_Error(E_Fetch_Access_Fault, PC_hi),
MemValue(ihi) => F_Base(append(ihi, ilo))
}
}
}
}
}
}
}
}
}
}
}
}
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