CS664 - LLVM tips

Compile C source to LLVM IR (generates foo.ll text file):

clang -S -emit-llvm foo.c

Compile LLVM IR to x86 ASM (generates foo.s text file):

llc foo.ll

Translate x86 ASM to binary object code (generates foo.o):

as foo.s -o foo.o

Link object code with C library (generates a.out, a binary executable).

clang foo.o

Yes, we’re invoking the C compiler, but asking it just to do the linking. It’s possible to invoke the linker directly (the command is ld) but that requires manually specifying a bunch of system-dependent libraries. It’s much easier to ask gcc to do it.

Some other tricks: instead of compiling and linking down to native code, we can just run the LLVM interpreter directly:

lli foo.ll