Summary of useful GHC options

The last part of this chapter collects options for GHC and the Runtime System into a concise reference. Let's start off with GHC.

Basic usage

These are some of the most often used general flags related to compilation with GHC:

• --make: Compile a multi-module program

• -j<n>: Parallel compilation

• -i, -e, runghc: Interactive and evaluation modes

• -fforce-recomp: Force recompilation

• -Wall: Turn on all code-level warnings

• -Werror: Turn all warnings into errors

• -freverse-errors: Print top-most error last

The LLVM backend

The LLVM route is the preferred compilation path for numeric code. It requires the LLVM libraries and a compatible system. The flags used to enable LLVM are:

• -fllvm: Compile via LLVM

• -optlo-O3: Enable optimizations in the LLVM backend

Turn optimizations on and off

GHC has a sophisticated optimization pipeline. Every optimization can be turned on and off separately, but that's rarely necessary. Good default sets of optimizations are enabled with the -O family...