LLVM debug tips
https://youtu.be/y4b-sgp6VYA?si=FBwXN-abkikLJwx0
cmake .. -GNinja \
-DCMAKE_BUILD_TYPE=Release \
-DLLVM_ENABLE_LLD=ON \
-DLLVM_ENABLE_PROJECTS="clang;lld;compiler-rt" \
-DLLVM_TARGETS_TO_BUILD="AArch64;ARM;X86" \
-DLLVM_ENABLE_ASSERTION=OFF
-E : Stop before compiling
-S : Stop before assembling
-c : Stop before linking
Dumping LEXER Tokens
clang -Xclang -dump-tokens -E foo.cpp
clang -Xclang -help -E foo.cpp
clang -Xclang -emit-html -o foo.html foo.cpp
clang -Xclang -asp-dump -E foo.cpp
// Only can be used in debug build
clang -Xclang -ast-view -E foo.cpp
Dumping LLVM IR
clang foo.cpp -emit-llvm -S -o - -fno-discard-value-names -g0
-emit-llvm : produce LLVM IR
-S : as human readable foo.ll, not binary foo.bc
-o - : output to stdout rather than to .ll or .bc. file
-fno-discard-value-names : identifiers from source rather than numbers
-g0 : less debug info in IR
clang -emit-llvm -S -O2 -Xclang -disable-llvm-passes foo.cpp
opt -O2 -s foo.ll
clang -emit-llvm -S -O2 foo.cpp
// print what happen during each pass
opt -O2 -print-after-all -S foo.cpp
LOWERING WITH LLC
llc foo.ll
llc -filetype=obj foo.ll
llc --print-after-all foo.ll
llc -debug-pass=Structure foo.ll
// PER PASS DEBUG INFO
opt -licm -debug-only=licm foo.ll -S -o -
clang -O2 -Rpass=licm -c foo.cpp
others, these option can be uses to clang with -mllvm prefixed
-print-after-all
-print-after=
-print-before-all
-print-before=
-stop-after=
-print-module-scope
-debug-pass=Arguments
//TABLE GEN
https://www.youtube.com/watch?v=45gmF77JFBY&ab_channel=FOSDEM
https://llvm.org/docs/TableGen/
TableGen Overview — LLVM 18.0.0git documentation
TableGen has a syntax that is loosely based on C++ templates, with built-in types and specification. In addition, TableGen’s syntax introduces some automation concepts like multiclass, foreach, let, etc. TableGen files consist of two key parts: ‘classe
llvm.org
https://llvm.org/docs/TableGen/BackEnds.html
TableGen BackEnds — LLVM 18.0.0git documentation
Warning This portion is incomplete. Each section below needs three subsections: description of its purpose with a list of users, output generated from generic input, and finally why it needed a new backend (in case there’s something similar). Overall, ea
llvm.org
https://llvm.org/docs/TableGen/BackEnds.html
TableGen BackEnds — LLVM 18.0.0git documentation
Warning This portion is incomplete. Each section below needs three subsections: description of its purpose with a list of users, output generated from generic input, and finally why it needed a new backend (in case there’s something similar). Overall, ea
llvm.org
https://llvm.org/docs/TableGen/ProgRef.html