Appendix B: Cpu0 document and test¶

Cpu0 document ¶

This section illustrates how to generate Cpu0 backend document.

LLVM and this book use Sphinx to generate html document. This book uses Sphinx to generate pdf and epub format of document further. The installation of Sphinx reference [1]. Sphinx uses restructured text format here [8] [9] [10]. About the code-block in this document, please reference [11] [12].

On iMac you can install as follows,

brew install sphinx-doc
echo 'export PATH="/opt/homebrew/opt/sphinx-doc/bin:$PATH"' >> ~/.zshrc
% source ~/.zshrc

On Linux install it as follows,

sudo apt-get install python3-sphinx

Above installaton for making html document but not for pdf. The following installation for making pdf/latex document.

On iMac, install MacTex.pkg from here [2] and restart computer.

On Linux, install texlive as follows,

sudo apt-get install texlive texlive-latex-extra latexmk

sudo yum install texlive texlive-latex-extra latexmk

On Fedora 17, the texlive-latex-extra is missing. We install the package which include the pdflatex instead. For instance, we install pdfjam on Fedora 17 as follows,

[root@localhost lbd]$ yum list pdfjam
Loaded plugins: langpacks, presto, refresh-packagekit
Installed Packages
pdfjam.noarch                        2.08-3.fc17                         @fedora
[root@localhost lbd]$

Do sudo apt-get update -y; sudo apt-get install -y latexmk; if latexmk error in ‘make latexpdf’ [3].

After upgrade to iMac OS X 10.11.1, pdflatex link is missing, fix it by set in .profile as follows,

114-37-153-62:lbd Jonathan$ ls /usr/local/texlive/2012/bin/universal-darwin/pdflatex
/usr/local/texlive/2012/bin/universal-darwin/pdflatex
114-37-153-62:lbd Jonathan$ cat ~/.profile
export PATH=$PATH:...:/usr/local/texlive/2012/bin/universal-darwin

Note of Sphinx ¶

Do not use > 90 characters in a line of code-block:: console or any code-block, otherwise it may show the error in make latexpdf.
Use “clearpage” (reference gpu.rst) to clear page for pdf to avoid split into two pages.

$HOME/git/lbd$ make latexpdf

Latexmk: applying rule 'pdflatex'...
Rule 'pdflatex': File changes, etc:
   Changed files, or newly in use since previous run(s):
  LLVMToolchainCpu0.aux
  LLVMToolchainCpu0.toc
Rule 'pdflatex': The following rules & subrules became out-of-date:
  pdflatex
Latexmk: Maximum runs of pdflatex reached without getting stable files
Latexmk: All targets (LLVMToolchainCpu0.pdf) are up-to-date
----------------------
This message may duplicate earlier message.
Latexmk: Failure in processing file 'LLVMToolchainCpu0.tex':
   'pdflatex' needed too many passes
----------------------
Latexmk: If appropriate, the -f option can be used to get latexmk
  to try to force complete processing.
make[1]: *** [LLVMToolchainCpu0.pdf] Error 12
make: *** [latexpdf] Error 2
make latexpdf  14.57s user 1.11s system 99% cpu 15.790 total

Sphinx support math symbols here [4] [5].

Note of graphviz ¶

Drawing nodes inside a parent node: “compound=true;”. Subgraph cluster_name [7]. Edge from/to parent node: “ltail/lhead = parent_node”.
Documents [6].

Generate Cpu0 document ¶

Cpu0 example code is added chapter by chapter. It can be configured to a specific chapter by change CH definition in Cpu0SetChapter.h. For example, the following definition configue it to chapter 2.

lbdex/Cpu0/Cpu0SetChapter.h

#define CH       CH2

To make readers easily understanding the backend structure step by step, Cpu0 example code can be generated with chapter by chapter through commands as follws,

118-165-12-177:lbd Jonathan$ pwd
/home/Jonathan/test/lbd
118-165-12-177:lbd Jonathan$ make genexample
...
118-165-12-177:lbd Jonathan$ ls lbdex/chapters/
Chapter10_1  Chapter2    Chapter3_4  Chapter5_1  Chapter8_2
Chapter11_1  Chapter3_1  Chapter3_5  Chapter6_1  Chapter9_1
Chapter11_2  Chapter3_2  Chapter4_1  Chapter7_1  Chapter9_2
Chapter12_1  Chapter3_3  Chapter4_2  Chapter8_1  Chapter9_3

Beside chapters example code, above html and pdf of Cpu0 documents also include files *.ll and *.s in lbd/lbdex/output.

JonathantekiiMac:lbd Jonathan$ ls lbdex/output/
ch12_eh.cpu0.s                        ch12_thread_var.cpu0.pic.s      ch12_thread_var.ll
ch12_eh.ll                    ch12_thread_var.cpu0.static.s   ch4_math.s

Then, this book html/pdf can be generated by the following commands.

118-165-12-177:lbd Jonathan$ pwd
/home/Jonathan/test/lbd
118-165-12-177:lbd Jonathan$ make html
...
118-165-12-177:lbd Jonathan$ make latexpdf
...

About Cpu0 document ¶

Since llvm have a new release version about every 6 months and every name of file, function, class, variable, …, etc, may be changed, the Cpu0 document maintains is an effort because it adds the code chapter by chapter. In order to make the document as correct and easily maintain. I use the “:start-after:” and “:end-before:” of restructured text format to keep the document update to date. For every new release, when the Cpu0 backend code is changed, the document will reflect the changes in most of the contents of document.

In lbdex/Cpu0, the text begin from “//@” and “#ifdef CH > CHxx” are refered by document files *.rst.

In lbdex/llvm/modify/llvm, the *.rst refer the code by copy them directly. Most of references exist in llvmstructure.rst and elf.rst.

The example C/C++ code in lbdex/input come from my thinking and refer the directory clang/test/CodeGen of clang source code release.

Cpu0 Regression Test ¶

The last chapter can verify Cpu0 backend’s generated code by Verilog simulator for those code without global variable access. The chapter lld in web https://github.com/Jonathan2251/lbt.git includes llvm ELF linker implementation and is capable of verifying those test items with global variable access. However, LLVM has its test cases (regression test) for each backend to verify your backend compiler [13] without implementing any simulator or real hardware platform. Cpu0 regression test items existed in lbdex.tar.gz example code. Untar it to lbdex/, and:

For both iMac and Linux, copy lbdex/regression-test/Cpu0 to ~/llvm/test/llvm/test/CodeGen/Cpu0.

Then run as follows for both of single and all test cases on iMac. The llvm-lit -a can display executing command.

1-160-130-77:Cpu0 Jonathan$ pwd
/Users/Jonathan/llvm/test/llvm/test/CodeGen/Cpu0
1-160-130-77:Cpu0 Jonathan$ ~/llvm/test/build/bin/llvm-lit seteq.ll
-- Testing: 1 tests, 1 threads --
PASS: LLVM :: CodeGen/Cpu0/seteq.ll (1 of 1)
Testing Time: 0.08s
  Expected Passes    : 1
1-160-130-77:Cpu0 Jonathan$ ~/llvm/test/build/bin/llvm-lit .
...
PASS: LLVM :: CodeGen/Cpu0/zeroreg.ll
PASS: LLVM :: CodeGen/Cpu0/tailcall.ll
...

Run as follows for test on Linux.

$ pwd
/home/cschen/llvm/test/llvm/test/CodeGen/Cpu0
$ ~/llvm/test/build/bin/llvm-lit seteq.ll
-- Testing: 1 tests, 1 threads --
PASS: LLVM :: CodeGen/Cpu0/seteq.ll (1 of 1)
Testing Time: 0.08s
  Expected Passes    : 1
$ ~/llvm/test/build/bin/llvm-lit .
...
PASS: LLVM :: CodeGen/Cpu0/zeroreg.ll
PASS: LLVM :: CodeGen/Cpu0/tailcall.ll
...

Listing the chapters of this book and the related regression test items as follows,

Table 48 Chapters¶
1	about
2	Cpu0 architecture and LLVM structure
3	Backend structure
4	Arithmetic and logic instructions
5	Generating object files
6	Global variables
7	Other data type
8	Control flow statements
9	Function call
10	ELF Support
11	Assembler
12	C++ support
13	Verify backend on verilog simulator

Table 49 Regression test items for Cpu0¶
File	v:pass x:fail	test ir, -> output asm	chapter
2008-06-05-Carry.ll	v		7
2008-07-15-InternalConstant.ll	v		6
2008-07-15-SmallSection.ll	v		6
2008-07-03-SRet.ll	v		9
2008-07-29-icmp.ll	v		8
2008-08-06-Alloca.ll	v		9
2008-08-01-AsmInline.ll	v		11
2008-08-08-ctlz.ll	v		7
2008-08-08-bswap.ll	v	bswap	12
2008-10-13-LegalizerBug.ll	v		8
2010-11-09-Mul.ll	v		4
2010-11-09-CountLeading.ll	v		7
2008-11-10-xint_to_fp.ll	v		7
addc.ll	v	64-bit add	7
addi.ll	v	32-bit add, sub	4
address-mode.ll	v	br, -> BB0_2:	8
alloca.ll	v	alloca i8, i32 %size, dynamic allocation	9
analyzebranch.ll	v	br, -> bne, beq	8
and1.ll	v	and	4
asm-large-immediate.ll	v	inline asm	11
atomic-1.ll	v	atomic	12
atomic-2.ll	v	atomic	12
atomics.ll	v	atomic	12
atomics-index.ll	v	atomic	12
atomics-fence.ll	v	atomic	12
br-jmp.ll	v	br, -> jmp	8
brockaddress.ll	v	blockaddress, -> lui, ori	8
cmov.ll	v	select, -> movn, movz	8
cprestore.ll	v	-> .cprestore	9
div.ll	v	sdiv, -> div, mflo	4
divrem.ll	v	sdiv, srem, udiv, urem, -> div, divu	4
div_rem.ll	v	sdiv, srem, -> div, mflo, mfhi	4
divu.ll	v	udiv, -> divu, mflo	4
divu_reml.ll	v	udiv, urem -> div, mflo, mfhi	4
double2int.ll	v	double to int, -> %call16(__fixdfsi)	7
eh-dwraf-cfa.ll	v		9
eh-return32.ll	v	Spill and reload all registers used for exception	9
eh.ll	v	c++ exception handling	12
ex2.ll	v	c++ exception handling	12
fastcc.ll	v	No effect in fastcc but can pass	9
fneg.ll	v	verify Cpu0 don’t uses hard float instruction	7
fp-spill-reload.ll	v	-> st $fp, ld $fp	9
frame-address.ll	v	addu $2, $zero, $fp	9
global-address.ll	v	global address, global variable	6
global-pointer.ll	v	global register load and retore, -> .cpload, .cprestore	9
gprestore.ll	v	global register retore, -> .cprestore	9
helloworld.ll	v	global register load and retore, -> .cpload, .cprestore	9
hf16_1.ll	v	function call in PIC, -> ld, jalr	9
i32k.ll	v	argument of constant int passing in register	9
i64arg.ll	v	argument of constant 64-bit passing in register	9
imm.ll	v	return constant 32-bit in register	9
indirectcall.ll	v	indirect function call	9
init-array.ll	v	check .init	6
inlineasm_constraint.ll	v	inline asm	11
inlineasm-cnstrnt-reg.ll	v		11
inlineasmmemop.ll	v		11
inlineasm-operand-code.ll	v		11
internalfunc.ll	v	internal function	9
jstat.ll	v	switch, -> JTI	8
lb1.ll	v	load i8*, sext i8, -> lb	7
lbu1.ll	v	load i8*, zext i8, -> lbu	7
lh1.ll	v	load i16*, sext i16, -> lh	7
lhu1.ll	v	load i16*, zext i16, -> lhu	7
llcarry.ll	v	64-bit add sub	7
longbranch.ll	v		8
machineverifier.ll	v	delay slot, (comment in machineverifier.ll)	8
mipslopat.ll	v	no check output (comment in mipslopat.ll)	6
misha.ll	v	miss alignment half word access	7
module-asm.ll	v	module asm	11
module-asm-cpu032II.ll	v	module asm	11
mul.ll	v	mul	4
mulll.ll	v	64-bit mul	4
mulull.ll	v	64-bit mul	4
not1.ll	v	not 1	4
null.ll	v	ret i32 0, -> ret $lr	3
o32_cc_byval.ll	v	by value	9
o32_cc_vararg.ll	v	variable argument	9
private.ll	v	private function call	9
rem.ll	v	srem, -> div, mfhi	4
remat-immed-load.ll	v	immediate load	3
remul.ll	v	urem, -> div, mfhi	4
return-vector-float4.ll	v	return vector, -> lui lui …	3
return-vector.ll	v	return vector, -> ld ld …, st st …	3
return_address.ll	v	llvm.returnaddress, -> addu $2, $zero, $lr	9
rotate.ll	v	rotl, rotr, -> rolv, rol, rorv	4
sb1.ll	v	store i8, sb	7
select.ll	v	select, -> movn, movz	8
seleq.ll	v	following for br with different condition	8
seleqk.ll	v		8
selgek.ll	v		8
selgt.ll	v		8
selle.ll	v		8
selltk.ll	v		8
selne.ll	v		8
selnek.ll	v		8
seteq.ll	v		8
seteqz.ll	v		8
setge.ll	v		8
setgek.ll	v		8
setle.ll	v		8
setlt.ll	v		8
setltk.ll	v		8
setne.ll	v		8
setuge.ll	v		8
setugt.ll	v		8
setule.ll	v		8
setult.ll	v		8
setultk.ll	v		8
sext_inreg.ll	v	sext i1, -> shl, sra	4
shift-parts.ll	v	64-bit shl, lshr, ashr, -> call function	9
shl1.ll	v	shl, -> shl	4
shl2.ll	v	shl, -> shlv	4
shr1.ll	v	shr, -> shr	4
shr2.ll	v	shr, -> shrv	4
sitofp-selectcc-opt.ll	v	comment in sitofp-selectcc-opt.ll	7
small-section-reserve-gp.ll	v	Cpu0 option -cpu0-use-small-section=true	6
sra1.ll	v	ashr, -> sra	4
sra2.ll	v	ashr, -> srav	4
stacksave-restore.ll	v		9
stacksize.ll	v	comment in stacksize.ll	9
stchar.ll	v	load and store i16, i8	7
stldst.ll	v	register sp spill	9
sub1.ll	v	sub, -> addiu	4
sub2.ll	v	sub, -> sub	4
tailcall.ll	v	tail call	9
tls.ll	v	ir thread_local global is for c++ “__thread int b;”	12
tls-alias.ll	v	thread_local global and thread local alias	12
tls-models.ll	v	ir external/internal thread_local global	12
uitofp.ll	v	integer2float, uitofp, -> jsub __floatunsisf	9
uli.ll	v	unalignment init, -> sb sb …	6
unalignedload.ll	v	unalignment init, -> sb sb …	6
vector-setcc.ll	v		7
weak.ll	v	extern_weak function, -> .weak	9
xor1.ll	v	xor, -> xor	4
zeroreg.ll	v	check register $zero	4

These supported test cases are in lbdex/regression-test/Cpu0 which can be gotten from tar -xf lbdex.tar.gz.

The regression test is useful in two major reasons. First, it provides the llvm input, assembly output and the running command as well as options in the the sample input file, so all the first glimpse of documentation needed for both end user and programmer are well written in the same test input file. Second, once programmers change their backend compiler especially for optimization, the regression testing may fail for some side effect or bugs from this new change. That is the name of “regression test” stands for. The following file includes the assembly output pattern of two subtargets for Cpu0 backend. Beside checking opcode, it is capable to check register number. In this case, the destination register of “andi” must be the first source register in the following instruction “xori” once it is specified to T1 at the corresponding registers of these two assembly output.

lbdex/regression-test/Cpu0/setule.ll

; RUN: llc  -march=cpu0 -mcpu=cpu032I  -relocation-model=pic -O3 %s -o - | FileCheck %s -check-prefix=cpu032I
; RUN: llc  -march=cpu0 -mcpu=cpu032II  -relocation-model=pic -O3 %s -o - | FileCheck %s -check-prefix=cpu032II

@j = global i32 5, align 4
@k = global i32 10, align 4
@l = global i32 20, align 4
@m = global i32 10, align 4
@r1 = common global i32 0, align 4
@r2 = common global i32 0, align 4
@r3 = common global i32 0, align 4

define void @test() nounwind {
entry:
  %0 = load i32, i32* @j, align 4
  %1 = load i32, i32* @k, align 4
  %cmp = icmp ule i32 %0, %1
  %conv = zext i1 %cmp to i32
  store i32 %conv, i32* @r1, align 4
; cpu032I:  cmp	$sw, ${{[0-9]+|t9}}, ${{[0-9]+|t9}}
; cpu032I:  andi	$[[T1:[0-9]+|t9]], $sw, 1
; cpu032I:  xori	${{[0-9]+|t9}}, $[[T1]], 1
; cpu032II:  sltu	$[[T0:[0-9]+|t9]], ${{[0-9]+|t9}}, ${{[0-9]+|t9}}
; cpu032II:  xori	${{[0-9]+|t9}}, $[[T0]], 1
  %2 = load i32, i32* @m, align 4
  %cmp1 = icmp ule i32 %2, %1
  %conv2 = zext i1 %cmp1 to i32
  store i32 %conv2, i32* @r2, align 4
  ret void
}

Run regression test must after build llvm. The following READ.rst and changes in related config files and llvm-lit allowing to setup llvm-lit for pre-build/ pre-installed llvm for running llvm-lit without build llvm.

lbdex/set-llvm-lit/README.txt

llvm-lit can be changed to support the installed clang/llvm. Then llvm-lit can
be run directly without build the clang/llvm.

## Run llvm-lit without building llvm-project

    $ pwd
    $ $HOME/test/llvm/llvm/test/CodeGen/Cpu0
    // change the following to dir for your llvm-project
    $ export LLVM_DIR=$HOME/test/llvm
    $ export LLVM_INSTALLED_DIR=$HOME/llvm-installed
    $ ~/llvm-installed/bin/llvm-lit addc.ll -a
    $ ~/llvm-installed/bin/llvm-lit .
    ~/test/llvm/clang/test/CodeGen/Cpu0$ ~/riscv/riscv_newlib/bin/llvm-lit . -a

set-llvm-lit % diff -r origin modify &> set-llvm-lit.diff

lbdex/set-llvm-lit/set-llvm-lit.diff

diff -r origin/bin/llvm-lit modify/bin/llvm-lit
8c8
< install_dir = r'/usr/local/riscv/andes/riscv_newlib'
---
> install_dir = os.environ["LLVM_INSTALLED_DIR"]
diff -r origin/test/Unit/lit.site.cfg.py modify/test/Unit/lit.site.cfg.py
3a4,9
> import os
> 
> llvm_project_dir = os.environ["PHOENIX_LLVM_DIR"]
> print('llvm_project_dir: ', llvm_project_dir)
> install_dir = os.environ["LLVM_INSTALLED_DIR"]
> 
4a11
> from pathlib import Path
7c14
<     return os.path.join(os.path.dirname(os.path.abspath(__file__)), p)
---
>     return str((Path(__file__).parent / p).resolve())
12,14c19,21
< config.llvm_src_root = path(r"/Users/cschen/llvm/test/llvm")
< config.llvm_obj_root = path(r"/Users/cschen/llvm/test/build")
< config.llvm_tools_dir = path(r"/Users/cschen/llvm/test/build/./bin")
---
> config.llvm_src_root = path(llvm_project_dir)+path(r"/llvm")
> config.llvm_obj_root = path(install_dir)
> config.llvm_tools_dir = path(install_dir)+path(r"/./bin")
17c24
< config.shlibdir = path(r"/Users/cschen/llvm/test/build/./lib")
---
> config.shlibdir = path(install_dir)+path(r"/./lib")
23a31
>     config.shlibdir = config.shlibdir % lit_config.params
diff -r origin/test/lit.site.cfg.py modify/test/lit.site.cfg.py
1c1
< # Autogenerated from /Users/cschen/llvm/test/llvm/test/lit.site.cfg.py.in
---
> # Autogenerated from /u/jonathanchen/andes/riscv/Phoenix/llvm-project/llvm/test/lit.site.cfg.py.in
3a4,9
> import os
> 
> llvm_project_dir = os.environ["PHOENIX_LLVM_DIR"]
> print('llvm_project_dir: ', llvm_project_dir)
> install_dir = r'/usr/local/riscv/andes/riscv_newlib'
> 
4a11
> from pathlib import Path
7c14
<     return os.path.join(os.path.dirname(os.path.abspath(__file__)), p)
---
>     return str((Path(__file__).parent / p).resolve())
12,19c19,27
< config.host_triple = "arm64-apple-darwin20.6.0"
< config.target_triple = "cpu0-unknown-elf"
< config.llvm_src_root = path(r"/Users/cschen/llvm/test/llvm")
< config.llvm_obj_root = path(r"/Users/cschen/llvm/test/build")
< config.llvm_tools_dir = path(r"/Users/cschen/llvm/test/build/./bin")
< config.llvm_lib_dir = path(r"/Users/cschen/llvm/test/build/./lib")
< config.llvm_shlib_dir = path(r"/Users/cschen/llvm/test/build/./lib")
< config.llvm_shlib_ext = ".dylib"
---
> config.host_triple = "x86_64-unknown-linux-gnu"
> config.target_triple = "riscv64-unknown-elf"
> config.llvm_src_root = path(llvm_project_dir)+path(r"/llvm")
> config.llvm_obj_root = path(install_dir)
> config.llvm_tools_dir = path(install_dir)+path(r"/./bin")
> config.llvm_lib_dir = path(install_dir)+path(r"/./lib")
> config.llvm_shlib_dir = path(install_dir)+path(r"/./lib")
> config.llvm_shlib_ext = ".so"
> config.llvm_plugin_ext = ".so"
22,24c30,34
< config.python_executable = "/opt/homebrew/Frameworks/Python.framework/Versions/3.9/bin/python3.9"
< config.gold_executable = "/opt/homebrew/bin/riscv64-unknown-elf-ld"
< config.ld64_executable = "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld"
---
> config.errc_messages = "No such file or directory;Is a directory;Invalid argument;Permission denied"
> config.python_executable = "/usr/bin/python3.6"
> config.gold_executable = "/usr/bin/ld.gold"
> config.ld64_executable = ""
> config.osx_sysroot = path(r"")
33,34c43,44
< config.targets_to_build = " Cpu0"
< config.native_target = "AArch64"
---
> config.targets_to_build = " RISCV"
> config.native_target = "X86"
36,38c46,48
< config.host_os = "Darwin"
< config.host_cc = "/opt/homebrew/opt/llvm/bin/clang "
< config.host_cxx = "/opt/homebrew/opt/llvm/bin/clang++ "
---
> config.host_os = "Linux"
> config.host_cc = "/usr/bin/cc "
> config.host_cxx = "/usr/bin/c++ "
44,45c54,55
< config.have_libxar = 1
< config.have_libxml2 = 1
---
> config.have_libxar = 0
> config.have_libxml2 = 0
52,53c62,63
< config.llvm_host_triple = 'arm64-apple-darwin20.6.0'
< config.host_arch = "arm64"
---
> config.llvm_host_triple = 'x86_64-unknown-linux-gnu'
> config.host_arch = "x86_64"
65a76
>     config.llvm_lib_dir = config.llvm_lib_dir % lit_config.params
diff -r origin/tools/clang/test/Unit/lit.site.cfg.py modify/tools/clang/test/Unit/lit.site.cfg.py
3a4,9
> import os
> 
> llvm_project_dir = os.environ["LLVM_DIR"]
> print('llvm_project_dir: ', llvm_project_dir)
> install_dir = os.environ["LLVM_INSTALLED_DIR"]
> 
4a11
> from pathlib import Path
7c14
<     return os.path.join(os.path.dirname(os.path.abspath(__file__)), p)
---
>     return str((Path(__file__).parent / p).resolve())
12,15c19,22
< config.llvm_src_root = path(r"/Users/cschen/llvm/test/llvm")
< config.llvm_obj_root = path(r"/Users/cschen/llvm/test/build")
< config.llvm_tools_dir = path(r"/Users/cschen/llvm/test/build/./bin")
< config.llvm_libs_dir = path(r"/Users/cschen/llvm/test/build/./lib")
---
> config.llvm_src_root = path(llvm_project_dir)+path(r"/llvm")
> config.llvm_obj_root = path(install_dir)
> config.llvm_tools_dir = path(install_dir)+path(r"/./bin")
> config.llvm_libs_dir = path(install_dir)+path(r"/./lib")
17c24
< config.clang_obj_root = path(r"/Users/cschen/llvm/test/build/tools/clang")
---
> config.clang_obj_root = path(install_dir)+path(r"/tools/clang")
19,20c26,27
< config.shlibdir = path(r"/Users/cschen/llvm/test/build/./lib")
< config.target_triple = "cpu0-unknown-elf"
---
> config.shlibdir = path(install_dir)+path(r"/./lib")
> config.target_triple = "riscv64-unknown-elf"
28a36
>     config.shlibdir = config.shlibdir % lit_config.params
36c44
<     config, os.path.join(path(r"/Users/cschen/llvm/test/clang"), "test/Unit/lit.cfg.py"))
---
>     config, os.path.join(path(llvm_project_dir)+path(r"/clang"), "test/Unit/lit.cfg.py"))
diff -r origin/tools/clang/test/lit.site.cfg.py modify/tools/clang/test/lit.site.cfg.py
3a4,9
> import os
> 
> llvm_project_dir = os.environ["LLVM_DIR"]
> print('llvm_project_dir: ', llvm_project_dir)
> install_dir = os.environ["LLVM_INSTALLED_DIR"]
> 
4a11
> from pathlib import Path
7c14
<     return os.path.join(os.path.dirname(os.path.abspath(__file__)), p)
---
>     return str((Path(__file__).parent / p).resolve())
12,17c19,24
< config.llvm_src_root = path(r"/Users/cschen/llvm/test/llvm")
< config.llvm_obj_root = path(r"/Users/cschen/llvm/test/build")
< config.llvm_tools_dir = path(r"/Users/cschen/llvm/test/build/./bin")
< config.llvm_libs_dir = path(r"/Users/cschen/llvm/test/build/./lib")
< config.llvm_shlib_dir = path(r"/Users/cschen/llvm/test/build/./lib")
< config.llvm_plugin_ext = ".dylib"
---
> config.llvm_src_root = path(llvm_project_dir)+path(r"/llvm")
> config.llvm_obj_root = path(install_dir)
> config.llvm_tools_dir = path(install_dir)+path(r"/./bin")
> config.llvm_libs_dir = path(install_dir)+path(r"/./lib")
> config.llvm_shlib_dir = path(install_dir)+path(r"/./lib")
> config.llvm_plugin_ext = ".so"
19,24c26,35
< config.clang_obj_root = path(r"/Users/cschen/llvm/test/build/tools/clang")
< config.clang_src_dir = path(r"/Users/cschen/llvm/test/clang")
< config.clang_tools_dir = path(r"/Users/cschen/llvm/test/build/./bin")
< config.host_triple = "arm64-apple-darwin20.6.0"
< config.target_triple = "cpu0-unknown-elf"
< config.host_cxx = "/opt/homebrew/opt/llvm/bin/clang++"
---
> config.errc_messages = "No such file or directory;Is a directory;Invalid argument;Permission denied"
> config.clang_lit_site_cfg = __file__
> config.clang_obj_root = path(install_dir)+path(r"/tools/clang")
> config.clang_src_dir = path(llvm_project_dir)+path(r"/clang")
> config.clang_tools_dir = path(install_dir)+path(r"/./bin")
> config.clang_lib_dir = path(install_dir)+path(r"/lib")
> config.host_triple = "x86_64-unknown-linux-gnu"
> config.target_triple = "riscv64-unknown-elf"
> config.host_cc = "/usr/bin/cc"
> config.host_cxx = "/usr/bin/c++"
34c45
< config.enable_experimental_new_pass_manager = 0
---
> config.enable_experimental_new_pass_manager = 1
36,37c47,48
< config.host_arch = "arm64"
< config.python_executable = "/opt/homebrew/Frameworks/Python.framework/Versions/3.9/bin/python3.9"
---
> config.host_arch = "x86_64"
> config.python_executable = "/usr/bin/python3.6"
40a52
> config.llvm_external_lit = path(r"")
diff -r origin/utils/lit/lit.site.cfg modify/utils/lit/lit.site.cfg
3a4,9
> import os
> 
> llvm_project_dir = os.environ["PHOENIX_LLVM_DIR"]
> print('llvm_project_dir: ', llvm_project_dir)
> install_dir = os.environ["LLVM_INSTALLED_DIR"]
> 
4a11
> from pathlib import Path
7c14
<     return os.path.join(os.path.dirname(os.path.abspath(__file__)), p)
---
>     return str((Path(__file__).parent / p).resolve())
13,15c20,22
< config.llvm_src_root = "/Users/cschen/llvm/test/llvm"
< config.llvm_obj_root = "/Users/cschen/llvm/test/build"
< config.llvm_tools_dir = "/Users/cschen/llvm/test/build/./bin"
---
> config.llvm_src_root = path(llvm_project_dir)+path(r"/llvm")
> config.llvm_obj_root = path(install_dir)
> config.llvm_tools_dir = path(install_dir)+path(r"/./bin")
30c37
< lit_config.load_config(config, "/Users/cschen/llvm/test/build/utils/lit/tests/lit.cfg")
---
> lit_config.load_config(config, os.path.join(config.llvm_obj_root, "utils/lit/tests/lit.cfg"))

Only tools/clang/test/lit.site.cfg.py and test/lit.site.cfg.py need to be modified. The other tools/clang/test/Unit/lit.site.cfg.py, test/Unit/lit.site.cfg.py and utils/lit/tests/lit.site.cfg.in are empty and useless. However I modify them either.

Tutorial: Creating an LLVM Backend for the Cpu0 Architecture