LLVM Options

This guide documents LLVM backend options available in solx through the --llvm-options flag.

Usage

Pass options as a single string after =:

solx contract.sol --llvm-options='-option1 value1 -option2 value2'

EVM Backend Options

These options are specific to the custom LLVM EVM backend and affect compilation behavior directly.

-evm-stack-region-size <value>

Sets the stack spill region size in bytes. The compiler uses this region to spill values that cannot remain on the EVM stack (stack-too-deep mitigation). Normally set automatically based on optimizer settings. Requires -evm-stack-region-offset to be set as well.

-evm-stack-region-offset <value>

Sets the stack spill region memory offset. Normally set automatically to match the solc user memory offset.

-evm-metadata-size <value>

Sets the metadata size hint used by the backend for gas and code size tradeoff decisions.

Standard LLVM Diagnostic Options

Standard LLVM diagnostic options can be passed through --llvm-options and their output is printed to stderr. Some options (such as -debug and -debug-only) require LLVM built with assertions enabled (-DLLVM_ENABLE_ASSERTIONS=ON). When building from source, pass --enable-assertions to solx-dev llvm build.

-time-passes

Print timing information for each LLVM pass.

solx contract.sol --bin --llvm-options='-time-passes'

-stats

Print statistics from LLVM passes (number of transformations applied, etc.).

-print-after-all

Print LLVM IR after every optimization pass. Produces very large output (tens of thousands of lines) but useful for tracing pass behavior.

-print-before-all

Print LLVM IR before every optimization pass.

-debug-only=<pass-name>

Enable debug output for a specific LLVM pass. Note that --llvm-debug-logging controls pass-builder logging specifically, not the general LLVM DEBUG() macro categories.

CLI Debug Flags

These are top-level solx flags (not passed through --llvm-options):

See the Debugging guide for the full set of diagnostic flags.