LLC(1)

💅 llc — the LLVM static compiler, bestie edition 💅

okay so you found the llc manpage and you're like "what even is this" — don't worry, I got you. This is the tea on llc from the LLVM manual, and we're gonna get through it together. No gatekeeping, periodt. ✨

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🌸 NAME 🌸

llc — the LLVM static compiler. That's the whole vibe.

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🦋 SYNOPSIS 🦋

llc [options] [filename]

literally just the command, some options, and a filename. iconic.

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💖 DESCRIPTION 💖

Okay so <pink>the llc command compiles LLVM source inputs into assembly language for a specified architecture</pink>. Slay. Then you can pass that assembly output through a native assembler and linker to generate a native executable. Chef's kiss. 👑

The way it picks which architecture to generate assembly for? <cyan>It's automatically determined from the input file</cyan>, unless you use -march to override the default. So you can let it vibe and decide for itself, or you can step in and be the main character. 🎀

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✨ OPTIONS ✨

Okay bestie, here's the important stuff about inputs and outputs first:

• If filename is "-" or omitted, llc reads from standard input. Otherwise, it reads from filename.
• Inputs can be in either the LLVM assembly language format (.ll) or the LLVM bitcode format (.bc).

Now for the output rules, which are lowkey a whole vibe check:

• If the -o option is omitted, llc sends its output to standard output <pink>if the input is from standard input</pink>.
• If -o specifies "-", the output also goes to standard output.
• If no -o is specified AND you gave an input file other than "-", then llc creates the output filename by <cyan>taking the input filename, removing any existing .bc extension, and adding a .s suffix</cyan>.

Other llc options are below, don't worry, I didn't forget a single one. 💅

⭐ End-user Options ⭐

• -help — Print a summary of command line options. cute little cheat sheet.
• -o <filename> — Use <filename> as the output filename. See the summary above for more details, iykyk.
• -O=uint — Generate code at different optimization levels. These correspond to the -O0, -O1, -O2, and -O3 optimization levels used by clang. Levels, bestie. pick ur fighter.
• -mtriple=<target triple> — Override the target triple specified in the input file with the specified string. take that, input file.
• -march=<arch> — Specify the architecture for which to generate assembly, overriding the target encoded in the input file. See the output of llc -help for a list of valid architectures. By default this is inferred from the target triple or autodetected to the current architecture.
• -mcpu=<cpuname> — Specify a specific chip in the current architecture to generate code for. By default this is inferred from the target triple and autodetected to the current architecture. For a list of available CPUs, use:

llvm-as < /dev/null | llc -march=xyz -mcpu=help

• -filetype=<output file type> — Specify what kind of output llc should generated. Options are: asm for textual assembly ('.s'), obj for native object files ('.o') and null for not emitting anything (for performance testing). Note that not all targets support all options.
• -mattr=a1,+a2,-a3,... — Override or control specific attributes of the target, such as whether SIMD operations are enabled or not. The default set of attributes is set by the current CPU. For a list of available attributes, use:

llvm-as < /dev/null | llc -march=xyz -mattr=help

• --frame-pointer — Specify effect of frame pointer elimination optimization (all,non-leaf,none).
• --disable-excess-fp-precision — Disable optimizations that may produce excess precision for floating point. Note that this option can dramatically slow down code on some systems (e.g. X86). dramatic and slow, just like me before coffee. 💀
• --enable-no-infs-fp-math — Enable optimizations that assume no Inf values.
• --enable-no-nans-fp-math — Enable optimizations that assume no NAN values.
• --enable-no-signed-zeros-fp-math — Enable FP math optimizations that assume the sign of 0 is insignificant. zero? irrelevant. 💅
• --enable-no-trapping-fp-math — Enable setting the FP exceptions build attribute not to use exceptions.
• --enable-unsafe-fp-math — Enable optimizations that make unsafe assumptions about IEEE math (e.g. that addition is associative) or may not work for all input ranges. These optimizations allow the code generator to make use of some instructions which would otherwise not be usable (such as fsin on X86). > risky math moves, bestie. it said unsafe for a reason, don't @ me.
• --stats — Print statistics recorded by code-generation passes.
• --time-passes — Record the amount of time needed for each pass and print a report to standard error.
• --load=<dso_path> — Dynamically load dso_path (a path to a dynamically shared object) that implements an LLVM target. This will permit the target name to be used with the -march option so that code can be generated for that target.
• -meabi=[default|gnu|4|5] — Specify which EABI version should conform to. Valid EABI versions are gnu, 4 and 5. Default value (default) depends on the triple.
• -stack-size-section — Emit the .stack_sizes section which contains stack size metadata. The section contains an array of pairs of function symbol values (pointer size) and stack sizes (unsigned LEB128). The stack size values only include the space allocated in the function prologue. Functions with dynamic stack allocations are not included.
• -remarks-section — Emit the __remarks (MachO) section which contains metadata about remark diagnostics.

🔧 Tuning/Configuration Options 🔧

• --print-after-isel — Print generated machine code after instruction selection (useful for debugging). debugging era. 🔍
• --regalloc=<allocator> — Specify the register allocator to use. Valid register allocators are:
  • basic — Basic register allocator.
  • fast — Fast register allocator. It is the default for unoptimized code.
  • greedy — Greedy register allocator. It is the default for optimized code. greedy for a reason, she wants it all. 👑
  • pbqp — Register allocator based on 'Partitioned Boolean Quadratic Programming'. yes that's a real name and yes it ate.
• --spiller=<spiller> — Specify the spiller to use for register allocators that support it. Currently this option is used only by the linear scan register allocator. The default spiller is local. Valid spillers are:
  • simple — Simple spiller
  • local — Local spiller

🧚 Intel IA-32-specific Options 🧚

• --x86-asm-syntax=[att|intel] — Specify whether to emit assembly code in AT&T syntax (the default) or Intel syntax. pick your aesthetic, bestie. ✨

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🌈 EXIT STATUS 🌈

If llc succeeds, it will exit with 0. Otherwise, if an error occurs, it will exit with a non-zero value. no cap, that's the whole status report. 🫶

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🍓 SEE ALSO 🍓

lli(1) — go check her out too, she's giving main character energy. 💜

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🎀 AUTHOR 🎀

Maintained by the LLVM Team (https://llvm.org/). protect them at all costs. 🫡

⭐ COPYRIGHT ⭐

2003-2023, LLVM Project. periodt. 💅

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okay that's the whole page, bestie!! 🦋💖✨

this iconic lil manpage is LLC(1) from the LLVM manual, dated 2023-12-01, page 17. go compile something cute with it. 🌸👑🎀