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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Started work on nPower. nPower is going to be a PowerPC compatible core. The plan is to use the LLVM toolchain for software. The initial core will be 32-bits, super-pipelined with two parallel pipelines executing in-order. Got the basic core coded with a simplified instruction set. When run in synthesis however, synthesis trims out most of the design leaving on 175 LUTs. I haven’t been able to figure out from the synthesis report where most of the trim is occurring, everything it reports are trimmed seems reasonable, so I am picking off warning messages one-by-one. The following instructions are supported in the initial version. They should be enough to run some simple programs. Code: # Currently Supported Instructions
ADD ADDI ADDIS LBZ LBZU LBZX LBZUX
SUBF LHZ LHZU LHZX LHZUX
CMP CMPI EXTB LWZ LWZU LWZX LWZUX
CMPL CMPLI EXTH STB STBU STBX STBUX
AND ANDI ANDIS STH STHU STHX STHUX
OR ORI ORIS STW STWU STWX STWUX
XOR XORI XORIS B BC BCCTR BCLR
SLW NEG
SRW
SRAW SRAWI
_________________Robert Finch http://www.finitron.ca
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| Sat Dec 05, 2020 5:10 am |
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joanlluch
Joined: Fri Mar 22, 2019 8:03 am
Posts: 328
Location: Girona-Catalonia
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Implementing a processor compatible with a well known architecture should certainly help with the toolchain. The LLVM compiler should work great !
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| Sat Dec 05, 2020 12:39 pm |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Quote: Implementing a processor compatible with a well known architecture should certainly help with the toolchain. The LLVM compiler should work great ! This is what I hope. Building LLVM will have its own challenges. A trimmed down compiler is needed, so modifications are likely. Figured out what caused most of the logic to be trimmed. A pipeline valid signal (rval) was not being propagated resulting a zero being assigned to it. With the one pipeline stage flagged as always invalid, the entire pipeline was trimmed out. Anyway, the core size is now coming back as 40,000 LUTs, much more realistic. Many more instructions are now supported. Virtual memory is not going to be supported. The system is envisioned to contain multiple PowerPC cores each with a dedicated main memory. Code: # Currently Supported Instructions
ADD ADDI ADDIS LBZ LBZU LBZX LBZUX MFCR MTCRF
SUBF LHZ LHZU LHZX LHZUX MFSPR MTSPR
CMP CMPI EXTB LWZ LWZU LWZX LWZUX MFLR MTLR
CMPL CMPLI EXTH STB STBU STBX STBUX MFCTR MTCTR
AND ANDI ANDIS STH STHU STHX STHUX MFXER MTXER
OR ORI ORIS STW STWU STWX STWUX MCRXR
XOR XORI XORIS B BC BCCTR BCLR
ANDC ORC CRAND CROR CRXOR
NAND NOR CRNAND CRNOR CREQV
EQV CRANDC CRORC
MULLI MULLW RLWIMI
SLW NEG RLWINM
SRW RLWNM
SRAW SRAWI
# Features Not Supported
- segment registers
- tlb <software>The first issue with building LLVM was the Windows SDK version. The build tools for Visual Studio 17 had to be installed as it will not build with Visual Studio 19. Then I scrapped that build and started a build using LLVM 11.0 which works with Visual Studio 19. The build went well until it was about 90% complete at which point the machine ran out of memory and the build had to be aborted. This is on a machine with 16GB ram + 4GB swap file. Closed everything down, rebooted the machine and restarted the build. Then the build hung trying to run configure on things rather than completing the aborted build. So, now clean has been run and the build restarted again. PowerPC 32-bit code is what (nano) nPower uses. In LLVM there is a project for PowerPC64 bit code. I am wondering if it can build 32-bit binary files. A file is needed that is a raw binary file that can be placed in ROM code. The reset address needs to be specifiable. Digging into the compiler options is another task to be done. In the meantime, some more work was done on the RTF64 project. A simple NOP testbench was created and run in simulation. The core could at least fetch and execute the NOP instructions. But something more sophisticated is required now. _________________Robert Finch http://www.finitron.ca
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| Sun Dec 06, 2020 4:17 am |
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joanlluch
Joined: Fri Mar 22, 2019 8:03 am
Posts: 328
Location: Girona-Catalonia
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Hi Rob, I can't really help with installing LLVM on windows as I did it on a mac computer using Cmake and Xcode (not without a lot of pain). The LLVM community seems to use something called "Ninja", but I became familiar with Xcode long ago and I guess I'm too old to start now learning yet another IDE, despite LLVM only supports Xcode partially. I guess that claimed compatibility with a number of platforms is typical to open source project, and it's generally true, but not without a lot of problems and nuances. Regarding PowerPC, you can get the supported CPUs by typing the following command in the terminal window: Code: clang --target=powerpc -print-supported-cpus For LLVM V10 I get the following output: Code: clang version 10.0.0 (https://github.com/llvm/llvm-project.git 4786e1f8362e35817ac6bbf5359bfe19f7253592)
Target: powerpc
Thread model: posix
InstalledDir: /Users/joan/LLVM-10/llvm-project/build/Debug/bin
Available CPUs for this target:
440
450
601
602
603
603e
603ev
604
604e
620
7400
7450
750
970
a2
a2q
e500
e500mc
e5500
g3
g4
g4+
g5
generic
ppc
ppc32
ppc64
ppc64le
pwr3
pwr4
pwr5
pwr5x
pwr6
pwr6x
pwr7
pwr8
pwr9
Use -mcpu or -mtune to specify the target's processor.
For example, clang --target=aarch64-unknown-linux-gui -mcpu=cortex-a35 So, it looks to me that there's quite a lot of choice and it should be possible to start with the subset of instructions supported by one of the earlier cpus. As per my experience, I found easier to use LLVM to output only assembly code, rather than binary or executable files. The problem with binaries is that you need to know their format and they require a 'linker' pass before they are ready for execution. I do not know your experience with these things, including link file and executable file formats, but mine is null, so that's why I avoided that and chose a slightly different route. With assembly files, you can create an assembler to your entire convenience, and generate your executable files from that. I found this approach easier and more flexible. If you want to follow this route, in the case of PowerPC, you can invoke the following commands: Code: clang --target=powerpc -mcpu=ppc32 -emit-llvm -S -Os queens.c The example here is the "queens.c" program that we discussed in the compilers thread. This command creates a human readable "queens.ll" file with the LLVM intermediate representation, which you don't need to really understand but it's useful to get a taste of the target independent optimisations that are performed. "-Os" is the optimisation specification that balances speed with code size. I found this is ok to avoid very long executables with all the loops unnecessarily unrolled and frankly totally unreadable assemblies. Then you can use the *.ll file with 'llc' to produce the "*.s" assembly output, like this: I tried to ran the above commands and got the following PowerPC assembly output from the "queens.c" code: queens.s Code: .text
.file "queens.c"
.globl print_board # -- Begin function print_board
.p2align 2
.type print_board,@function
print_board: # @print_board
.Lfunc_begin0:
# %bb.0: # %entry
lis 5, 0
li 4, 0
li 6, 8
li 7, 81
li 8, 46
ori 5, 5, 65535
li 9, 10
mr 10, 3
.LBB0_1: # %for.cond1.preheader
# =>This Loop Header: Depth=1
# Child Loop BB0_2 Depth 2
slwi 11, 4, 5
add 11, 3, 11
addi 11, 11, -4
mtctr 6
.LBB0_2: # %for.body3
# Parent Loop BB0_1 Depth=1
# => This Inner Loop Header: Depth=2
lwzu 12, 4(11)
cmplwi 12, 0
bc 12, 2, .LBB0_4
# %bb.3: # %for.body3
# in Loop: Header=BB0_2 Depth=2
ori 12, 7, 0
b .LBB0_5
.LBB0_4: # %for.body3
# in Loop: Header=BB0_2 Depth=2
addi 12, 8, 0
.LBB0_5: # %for.body3
# in Loop: Header=BB0_2 Depth=2
stb 12, 0(5)
bdnz .LBB0_2
# %bb.6: # %for.end
# in Loop: Header=BB0_1 Depth=1
addi 4, 4, 1
cmplwi 4, 8
addi 10, 10, 32
stb 9, 0(5)
bne 0, .LBB0_1
# %bb.7: # %for.end7
li 3, 10
stb 3, 0(5)
stb 3, 0(5)
blr
.Lfunc_end0:
.size print_board, .Lfunc_end0-.Lfunc_begin0
# -- End function
.globl conflict # -- Begin function conflict
.p2align 2
.type conflict,@function
conflict: # @conflict
.Lfunc_begin1:
# %bb.0: # %entry
cmpwi 4, 1
blt 0, .LBB1_8
# %bb.1: # %for.body.preheader
subf 7, 4, 5
add 6, 5, 4
slwi 5, 5, 2
addi 8, 3, -32
slwi 9, 7, 2
add 5, 8, 5
add 8, 9, 8
slwi 9, 6, 2
add 3, 9, 3
addi 8, 8, -4
addi 9, 3, -28
mtctr 4
.LBB1_2: # %for.body
# =>This Inner Loop Header: Depth=1
lwzu 3, 32(5)
cmplwi 3, 0
li 3, 1
bnelr 0
# %bb.3: # %if.end
# in Loop: Header=BB1_2 Depth=1
cmpwi 7, 0
addi 8, 8, 36
blt 0, .LBB1_5
# %bb.4: # %if.then4
# in Loop: Header=BB1_2 Depth=1
lwz 4, 0(8)
cmplwi 4, 0
bnelr 0
.LBB1_5: # %if.end11
# in Loop: Header=BB1_2 Depth=1
cmpwi 6, 7
addi 9, 9, 28
bgt 0, .LBB1_7
# %bb.6: # %if.then14
# in Loop: Header=BB1_2 Depth=1
lwz 4, 0(9)
cmplwi 4, 0
bnelr 0
.LBB1_7: # %for.inc.critedge
# in Loop: Header=BB1_2 Depth=1
addi 6, 6, -1
addi 7, 7, 1
bdnz .LBB1_2
.LBB1_8:
li 3, 0
blr
.Lfunc_end1:
.size conflict, .Lfunc_end1-.Lfunc_begin1
# -- End function
.globl solve # -- Begin function solve
.p2align 2
.type solve,@function
solve: # @solve
.Lfunc_begin2:
# %bb.0: # %entry
mflr 0
stw 0, 4(1)
stwu 1, -48(1)
stw 30, 40(1) # 4-byte Folded Spill
cmplwi 4, 8
mr 30, 3
stw 23, 12(1) # 4-byte Folded Spill
stw 24, 16(1) # 4-byte Folded Spill
stw 25, 20(1) # 4-byte Folded Spill
stw 26, 24(1) # 4-byte Folded Spill
stw 27, 28(1) # 4-byte Folded Spill
stw 28, 32(1) # 4-byte Folded Spill
stw 29, 36(1) # 4-byte Folded Spill
bne 0, .LBB2_9
# %bb.1: # %for.cond1.preheader.i.preheader
lis 4, 0
li 3, 0
li 5, 8
li 6, 81
li 7, 46
ori 4, 4, 65535
li 8, 10
mr 9, 30
.LBB2_2: # %for.cond1.preheader.i
# =>This Loop Header: Depth=1
# Child Loop BB2_3 Depth 2
slwi 10, 3, 5
add 10, 30, 10
addi 10, 10, -4
mtctr 5
.LBB2_3: # %for.body3.i
# Parent Loop BB2_2 Depth=1
# => This Inner Loop Header: Depth=2
lwzu 11, 4(10)
cmplwi 11, 0
bc 12, 2, .LBB2_5
# %bb.4: # %for.body3.i
# in Loop: Header=BB2_3 Depth=2
ori 11, 6, 0
b .LBB2_6
.LBB2_5: # %for.body3.i
# in Loop: Header=BB2_3 Depth=2
addi 11, 7, 0
.LBB2_6: # %for.body3.i
# in Loop: Header=BB2_3 Depth=2
stb 11, 0(4)
bdnz .LBB2_3
# %bb.7: # %for.end.i
# in Loop: Header=BB2_2 Depth=1
addi 3, 3, 1
cmplwi 3, 8
addi 9, 9, 32
stb 8, 0(4)
bne 0, .LBB2_2
# %bb.8: # %print_board.exit
li 3, 10
stb 3, 0(4)
stb 3, 0(4)
b .LBB2_13
.LBB2_9: # %for.cond.preheader
slwi 26, 4, 5
add 3, 30, 26
mr 29, 4
addi 28, 4, 1
li 25, 0
li 24, 1
addi 23, 3, -4
li 27, 0
.LBB2_10: # %for.body
# =>This Inner Loop Header: Depth=1
mr 3, 30
mr 4, 29
mr 5, 27
addi 23, 23, 4
bl conflict
cmplwi 3, 0
bne 0, .LBB2_12
# %bb.11: # %if.then3
# in Loop: Header=BB2_10 Depth=1
mr 3, 30
mr 4, 28
stw 24, 0(23)
bl solve
stw 25, 0(23)
.LBB2_12: # %for.inc
# in Loop: Header=BB2_10 Depth=1
addi 27, 27, 1
cmplwi 27, 8
addi 26, 26, 4
bne 0, .LBB2_10
.LBB2_13: # %return
lwz 30, 40(1) # 4-byte Folded Reload
lwz 29, 36(1) # 4-byte Folded Reload
lwz 28, 32(1) # 4-byte Folded Reload
lwz 27, 28(1) # 4-byte Folded Reload
lwz 26, 24(1) # 4-byte Folded Reload
lwz 25, 20(1) # 4-byte Folded Reload
lwz 24, 16(1) # 4-byte Folded Reload
lwz 23, 12(1) # 4-byte Folded Reload
lwz 0, 52(1)
addi 1, 1, 48
mtlr 0
blr
.Lfunc_end2:
.size solve, .Lfunc_end2-.Lfunc_begin2
# -- End function
.globl main # -- Begin function main
.p2align 2
.type main,@function
main: # @main
.Lfunc_begin3:
# %bb.0: # %entry
mflr 0
stw 0, 4(1)
stwu 1, -16(1)
lis 3, board@ha
stw 30, 8(1) # 4-byte Folded Spill
la 30, board@l(3)
li 4, 0
mr 3, 30
li 5, 256
bl memset@PLT
mr 3, 30
li 4, 0
bl solve
li 3, 0
lwz 30, 8(1) # 4-byte Folded Reload
lwz 0, 20(1)
addi 1, 1, 16
mtlr 0
blr
.Lfunc_end3:
.size main, .Lfunc_end3-.Lfunc_begin3
# -- End function
.type board,@object # @board
.comm board,256,4
.ident "clang version 10.0.0 (https://github.com/llvm/llvm-project.git 4786e1f8362e35817ac6bbf5359bfe19f7253592)"
.section ".note.GNU-stack","",@progbits
I don't know much about the PowerPC, but the assembly file looks ok to me. This file of course must be assembled now to produce the final executable. This procedure worked fine for me, except that I implemented my own "CPU74" backend instead of using an existing one. Now, if you chose to follow a similar route and create your own assembler, then you don't even need to be byte compatible with the PowerPC, as far as your assembler understands all the supported PowerPC assembly mnemonics and patterns. I hope this helps Joan
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| Sun Dec 06, 2020 11:41 am |
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robinsonb5
Joined: Wed Nov 20, 2019 12:56 pm
Posts: 92
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This is where I sound like a broken record and recommend VBCC again (provided you don't mind the weird license). Vasm, too, if you need an assembler. It already has a PowerPC backend, it's relatively easy to modify, can be rebuilt in seconds after making a change, and doesn't take the form of a 30-foot-high teetering stack of semi-relevant layers, frameworks and build-tools that may or may not build successfully if your distro is too old or too new. (Wasted a lot of time this weekend trying to get a GCC-based ESP8266 toolchain up and running. I'm slightly annoyed by it - can you tell?  )
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| Sun Dec 06, 2020 4:46 pm |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Quote: Regarding PowerPC, you can get the supported CPUs by typing the following command in the terminal window: Thanks, I see there seems to be a lot of support for the PowerPC. The build environment settings in Visual Studio needed to be modified to reduce the amount of parallel build operations that occur. It was setup by default to be maxed out for my workstation, causing it to launch tools (cl, link) until the machine ran out of memory. I’ve had to restart the build several times as it runs into memory issues. Hopefully once the everything is built, building the specific tools wont be so troublesome. I did manage to get LLVM and CLANG built and compiled a “Hello World1” program for the PowerPC. Then I got stuck on how to convert it to a rom image. It is a toss up as to whether to proceed with LLVM or VBCC. Quote: This is where I sound like a broken record and recommend VBCC again (provided you don't mind the weird license). Vasm, too, if you need an assembler.
It already has a PowerPC backend, it's relatively easy to modify, can be rebuilt in seconds after making a change, and doesn't take the form of a 30-foot-high teetering stack of semi-relevant layers, frameworks and build-tools that may or may not build successfully if your distro is too old or too new. (Wasted a lot of time this weekend trying to get a GCC-based ESP8266 toolchain up and running. I'm slightly annoyed by it - can you tell? ) All very good points making vbcc worth looking into. I downloaded and fiddled around with VBCC yesterday until I got it to generate PowerPC code. But the download link for vasm does not work. It times out from my workstation. I want to modify the compiler to support features of the cc64 language, so VBCC may be easier to modify. _________________Robert Finch http://www.finitron.ca
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| Mon Dec 07, 2020 3:45 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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I had to modify the makefile for VBCC to get it to build using nmake. The command shell outs did not like the forward slashes in file paths so they all had to be converted to back-slashes to work. Also, when executing tools in bin they had to be referenced as .\bin otherwise they were not found. So, there were some minor mods to the makefile.
Still cannot download VASM. I left an email at the site.
_________________Robert Finch http://www.finitron.ca
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| Tue Dec 08, 2020 3:55 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Latest Milestone:
A compiled and assembled ROM test image.
<hardware> The reset address was modified to $FFFC0000 from $FFFFFFFC. This allows a smaller rom image to be used.
<software> The instruction bytes output by vasm for a binary file are output in the wrong order. The simplest fix was to provide an option in the processor core to reverse the order of the bytes.
A small utility bin2ver was written to convert binary files to Verilog memory assignment statements.
_________________Robert Finch http://www.finitron.ca
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| Thu Dec 10, 2020 4:03 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Just wading through the debug of nPower today. Many, many small fixes. Running in the simulator the first few lines of code execute okay, then there is a forwarding issue of some sort. Mulling over the idea of changing the design to a single pipeline, the results forwarding for the dual pipeline is pretty complex. Complicated by the load/store with update instructions. There are two sets of values to forward, the results bus and the effective address bus, resulting in about 16:1 multiplexors for forwarding. This is the current ROM test program: Code: int main()
{
int DBGAttr;
int* pLEDS = 0xFFDC0600;
int* pScreen = 0xFFD00000;
*pLEDS = 0xAA;
DBGAttr = 0x4FF0F000;
pScreen[0] = DBGAttr|'A';
pScreen[1] = DBGAttr|'A';
pScreen[2] = DBGAttr|'A';
pScreen[3] = DBGAttr|'A';
}
Which stops working correctly here: Code: .file "rom_bios.c"
.text
.align 2
.sdreg r13
.align 4
.global _main
_main:
stwu r1,-32(r1)
lis r11,-36
addi r11,r11,1536
stw r11,12(r1)
lis r11,-48
stw r11,16(r1)
li r11,170
lwz r12,12(r1)
-> stw r11,0(r12) <- this fails
lis r11,20465
addi r11,r11,-4096
stw r11,8(r1)
lwz r11,8(r1)
ori r0,r11,65
lwz r11,16(r1)
stw r0,0(r11)
lwz r11,8(r1)
ori r10,r11,65
lwz r9,16(r1)
stw r10,4(r9)
lwz r11,8(r1)
ori r10,r11,65
lwz r9,16(r1)
stw r10,8(r9)
lwz r11,8(r1)
ori r10,r11,65
lwz r9,16(r1)
stw r10,12(r9)
l1:
addi r1,r1,32
blr
.type _main,@function
.size _main,$-_main
# stacksize=32
.set ___stack_main,32
_________________Robert Finch http://www.finitron.ca
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| Fri Dec 11, 2020 5:00 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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I have not been able to resolve the forwarding issue in nPower yet, so it is going to be shelved for a few days. It does not forward an address from a previous instruction properly, causing the address zero to be used instead. One would think knowing roughly what the issue is it should be solvable. But it is complicated, occurring when two instructions are paired and a pipeline bubble needs to be inserted with a delay of the second pipeline. The bubble can be seen to be inserted by noting the advancement of the instruction register to the next stage, however the operands are not advanced properly, they appear to get left behind. It needs a double bubble in this case because it is the result of a load operation that needs to be bypassed. IFAICT it should be working. The logic is in place but I have missed something.
_________________Robert Finch http://www.finitron.ca
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| Sat Dec 12, 2020 4:20 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Tentatively solved the forwarding issue, but another issue cropped up. This time in the instruction fetch / icache. It is missing a pair of instructions on a cache load.
_________________Robert Finch http://www.finitron.ca
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| Sun Dec 13, 2020 5:48 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Latest Milestone: test program run in simulation.
Latest Fixes:
Much to my disbelief the register fields for logic and shift operations are swapped for Rt and Ra compared to the rest of the instruction set. I have a book that indicates this, but I had thought it was a transcription issue after reading the Open PowerPC docs. In newer versions of the processor the register fields are not swapped around.
After fixing this, the test program runs in simulation !
Now to move on to more complex tests.
_________________Robert Finch http://www.finitron.ca
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| Sun Dec 13, 2020 7:43 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Latest Milestone: now running Sieve of Eratosthenes
Many bug fixes later:
It looks like the IPC is turning out to be about 0.1. The best IPC that can be achieved with this design is 0.6666. The core stalls a lot of the time. The stall conditions are maybe too stringent in the interest of simplicity. The conditions are a dozen lines of combo logic.
_________________Robert Finch http://www.finitron.ca
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| Mon Dec 14, 2020 4:42 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Latest Mods:
<hardware> Added dual perceptron branch predictors, one for each pipe. With branch predictors and a couple of other minor tweaks, the IPC is now about 0.12, or almost 20% better. Further tweaking of the core has got it to 0.203 IPC for the Sieve program.
Support for even more of the instruction set has been added.
Testing:
A trivial test program was created containing a looping sequence of about 100 add instructions without any loads or stores. The core was able to achieve 1.75 instructions per machine cycle (a machine cycle being three clocks).
Latest Fixes:
<hardware> The value zero was not being returned if register zero was specified for Ra in the ADDI instruction. For loads and stores and ADDI if Ra is specified as zero then the value zero should be used. Otherwise r0 is just another general-purpose register.
_________________Robert Finch http://www.finitron.ca
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| Tue Dec 15, 2020 5:16 am |
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DiTBho
Joined: Sun Dec 20, 2020 1:54 pm
Posts: 74
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robfinch wrote: Code: # Currently Supported Instructions
ADD ADDI ADDIS LBZ LBZU LBZX LBZUX
SUBF LHZ LHZU LHZX LHZUX
CMP CMPI EXTB LWZ LWZU LWZX LWZUX
CMPL CMPLI EXTH STB STBU STBX STBUX
AND ANDI ANDIS STH STHU STHX STHUX
OR ORI ORIS STW STWU STWX STWUX
XOR XORI XORIS B BC BCCTR BCLR
SLW NEG
SRW
SRAW SRAWI
hi, very nice project! I have being playing with PPC4xx embedded cores for hobby since 2005, and I'd love to replace the physical chip with an FPGA because nowadays these chips are difficult to find, as well as eval-boards in good working conditions. I just wonder: is your subset the minimal operative set that you have distilled? Or are you going to extend it as soon as your code got a stable milestone? Thanks for sharing
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| Sun Dec 20, 2020 2:03 pm |
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