The LLVM Language Reference Manual has a "Hello world" example that uses the C run-time library.

I wanted a bare-bones example, using only the Win32 API, without a CRT dependency. Here it is:
  @.str = private unnamed_addr constant [13 x i8] c"Hello world\0A\00"

 declare i64 @GetStdHandle(i32) nounwind
 declare i32 @WriteFile(i64, i8* nocapture, i32, i32* nocapture, i8*) nounwind

 define i32 @Entry() {
 %hwStr = getelementptr [13 x i8]* @.str, i64 0, i64 0
 %handle = call i64 @GetStdHandle(i32 -11)
 %bytes = alloca i32
 call i32 @WriteFile(i64 %handle, i8* %hwStr, i32 12, i32* %bytes, i8* null)
 ret i32 2
 }
Compile and link steps:
  llc -filetype=obj hw.ll
 link hw.obj kernel32.lib /entry:Entry /subsystem:console
The resulting executable has 2,560 bytes, prints "Hello world", and returns exit code 2.

My main observation is that the language is clumsy. It's meant to be read by humans, but in most cases, generated automatically:
  1. No syntax for hexadecimal integers. If you want to enter a value like 0xC0000005 – good luck! :-)
  2. The types of all values have to be explicitly qualified each time they're used. This is irritating when writing, but may serve as useful documentation when reading.
  3. Interestingly, there's no "address-of" operator. Instead, alloca creates space for a value on the stack, and gives you the address. Neat!