This incorporates the fix made to Piccolo and Flute to not trap on
C.FLWSP/C.FLDSP when rd == 0; unlike the compressed stack pointer
relative integer loads/stores, these are legal, since f0 is a real FPR
rather than a constant zero.
>----------------
Status and outlook:
For RV64GC, out of 229 standard ISA tests, 202 PASS, 27 FAIL.
Below is a list of current failures, current diagnoses, and outlook.
'C' instructions:
rv64uc-v-rvc
Diagnosis: error in saved regs during instruction page fault
when a 32-bit instruction straddles a page boundary and
the second 16-bits encounters a page fault.
Note: the corresponding rv64uc-p-rvc passes, containing
the same set of tests except for the virtual-memory
aspect, so we expect this test to pass once this issue is
fixed.
Outlook: Target date for fix: 2019-Apr-09 (today)
System instructions:
rv64mi-p-access
rv64mi-p-csr
rv64si-p-dirty
rv64mi-p-illegal
Diagnosis: we do not have accurate diagnoses yet, although
some symptoms look similar to what we saw with earlier
processors (these test various corner-cases of system
instructions).
Outlook: Target date for fix: 2019-Apr-15
'F' and 'D' instructions
rv64uf-p-fadd rv64uf-v-fadd
rv64uf-p-fcmp rv64uf-v-fcmp
rv64uf-p-fdiv rv64uf-v-fdiv
rv64uf-p-fmin rv64uf-v-fmin
rv64ud-p-fadd rv64ud-v-fadd
rv64ud-p-fcmp rv64ud-v-fcmp
rv64ud-p-fdiv rv64ud-v-fdiv
rv64ud-p-fmadd rv64ud-v-fmadd
rv64ud-p-fmin rv64ud-v-fmin
rv64ud-p-ldst rv64ud-v-ldst
rv64ud-p-move rv64ud-v-move
Diagnosis: These seem to be simulation-only errors. Simulation
uses some quick-and-dirty floating-point "model" modules
written by the MIT authors, which are not accurate. All
the errors seem to be regarding incomplete treatment of
NaNs in the models. These errors should not happen in
FPGA since those use Xilinx IP modules instead. MIT has
been booting Linux with the Xilinx IP modules, lending
more confidence in the FPGA version.
The actual number of root-cause failures is likely to be
smaller than the list. For example, the 'fadd' test has
four variants: {uf/ud} x {-p-/-v-}; they all likely need a
comon fix.
Outlook: Target date: 2019-Apr-30
[Lower priority, since FPGA versions should be ok even now.]
>----------------
Detailed comments on file changes
New files:
Doc/micro2018.pdf
MIT's paper on RISCY-OOO at IEEE Micro
src_Core/CPU/CPU_Decode_C.bsv
Function to expand 'C' instrs to 32-bit counterparts, taken from Piccolo/Flute
Modified files:
src_Core/CPU/Core.bsv
Added rob_getOrig_Inst method
src_Core/RISCY_OOO/procs/RV64G_OOO/AluExePipeline.bsv
Added 'orig_inst' stuff, $displays
src_Core/RISCY_OOO/procs/RV64G_OOO/CommitStage.bsv
Mostly verbosity stuff, including printing out brief instruction trace similar to Piccolo/Flute.
src_Core/RISCY_OOO/procs/RV64G_OOO/FetchStage.bsv
Major changes for 'C', including call to Decode_C function from Piccolo/Flute
Pass orig_inst to downpipe.
src_Core/RISCY_OOO/procs/RV64G_OOO/RenameStage.bsv
Added 'orig_inst', input from FetchStage and passed on to ROB
Tweaked PC+4 check to accommodate 'C' instructions.
src_Core/RISCY_OOO/procs/lib/BrPred.bsv
Fixed 'decodeBrPred' to accommodate 'C' instructions
src_Core/RISCY_OOO/procs/lib/Exec.bsv
Fixed 'brAddrCalc', 'getControlFlow', 'basicExec' to acommodate 'C' instructions
src_Core/RISCY_OOO/procs/lib/MemLoader.bsv
Switched off 'verbose' by default
src_Core/RISCY_OOO/procs/lib/ProcTypes.bsv
Added 'C' to MISA, 'getExtensionBits'
src_Core/RISCY_OOO/procs/lib/ReorderBuffer.bsv
Added 'orig_inst' register to basic cell, and methods to set/access.
src_Core/RISCY_OOO/procs/lib/Types.bsv
Added typedefs for 'C' instructions
>----------------
