diff --git a/Cargo.lock b/Cargo.lock
index 0bd136ae08..c0774939ec 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -568,6 +568,10 @@ dependencies = [
  "roc_types",
 ]
 
+[[package]]
+name = "roc_builtins_bitcode"
+version = "0.1.0"
+
 [[package]]
 name = "roc_can"
 version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 9a713fbff2..07de563bac 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ members = [
     "compiler/types",
     "compiler/uniq",
     "compiler/builtins",
+    "compiler/builtins/bitcode",
     "compiler/constrain",
     "compiler/unify",
     "compiler/solve",
diff --git a/compiler/builtins/bitcode/Cargo.toml b/compiler/builtins/bitcode/Cargo.toml
new file mode 100644
index 0000000000..29ec5e72e0
--- /dev/null
+++ b/compiler/builtins/bitcode/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "roc_builtins_bitcode"
+version = "0.1.0"
+authors = ["Richard Feldman <richard.t.feldman@gmail.com>"]
+repository = "https://github.com/rtfeldman/roc"
+readme = "README.md"
+edition = "2018"
+description = "Generate LLVM bitcode for Roc builtins"
+license = "Apache-2.0"
+
diff --git a/compiler/builtins/bitcode/README.md b/compiler/builtins/bitcode/README.md
new file mode 100644
index 0000000000..1757864c88
--- /dev/null
+++ b/compiler/builtins/bitcode/README.md
@@ -0,0 +1,53 @@
+# Bitcode for Builtins
+
+Roc's builtins are implemented in the compiler using LLVM only.
+When their implementations are simple enough (e.g. addition), they
+can be implemented directly in Inkwell.
+
+When their implementations are complex enough, it's nicer to
+implement them in a higher-level language like Rust, compile the
+result to LLVM bitcode, and import that bitcode into the compiler.
+
+Here is the process for doing that.
+
+## Building the bitcode
+
+The source we'll use to generate the bitcode is in `src/lib.rs` in this directory.
+
+To generate the bitcode, `cd` into `compiler/builtins/bitcode/` and run:
+
+```bash
+$ cargo rustc --release --lib -- --emit=llvm-bc
+```
+
+Then look in the root `roc` source directory under `target/release/deps/` for a file
+with a name like `roc_builtins_bitcode-8da0901c58a73ebf.bc` - except
+probably with a different hash before the `.bc`. There should be only one `*.bc` file in that directory.
+
+> If you want to take a look at the human-readable LLVM IR rather than the
+> bitcode, run this instead and look for a `.ll` file instead of a `.bc` file:
+>
+> ```bash
+> $ cargo rustc --release --lib -- --emit=llvm-ir
+> ```
+
+## Importing the bitcode
+
+The bitcode is a bunch of bytes that aren't particularly human-readable.
+Since Roc is designed to be distributed as a single binary, these bytes
+need to be included in the raw source somewhere.
+
+We have a script that generates this file and writes it to stdout.
+To use it, run this command, replacing `bitcode.bc` with the path to the
+generated file in `target/release/deps/` from earlier.
+
+`$ ./import.pl bitcode.bc > ../../gen/src/llvm/builtins.rs`
+
+If the script succeeds, `git status` should show that the appropriate
+`.rs` file has been updated.
+
+Before checking it in, make sure to run `cargo fmt` on the root of
+the project! Otherwise that file will not be formatted properly and
+will fail the build.
+
+Once you've formatted the `builtins.rs` file, check it in and you're done!
diff --git a/compiler/builtins/bitcode/bitcode.bc b/compiler/builtins/bitcode/bitcode.bc
new file mode 100644
index 0000000000..f0d79e6208
Binary files /dev/null and b/compiler/builtins/bitcode/bitcode.bc differ
diff --git a/compiler/builtins/bitcode/import.pl b/compiler/builtins/bitcode/import.pl
new file mode 100755
index 0000000000..2af8e2e7ef
--- /dev/null
+++ b/compiler/builtins/bitcode/import.pl
@@ -0,0 +1,40 @@
+#!/usr/bin/perl
+
+$num_args = $#ARGV + 1;
+
+if ($num_args != 1) {
+    die "\nUsage: import.pl path-to-roc_builtins_bitcode-hashgoeshere.bc\n";
+}
+
+my $filename = $ARGV[0];
+my $before_bitcode = "// GENERATED FILE - NEVER EDIT BY HAND!\n//\n// See compiler/builtins/bitcode/README.md for how to generate.\n\npub const BUILTINS_BITCODE: &'static [u8] = &[\n    ";
+my $after_bitcode = "\n];";
+
+# Get a filehandle to the raw binary data in the file
+open(my $fh, '<:raw', $filename)
+    or die "Could not open file '$filename'\n\n$!";
+
+my $bitcode = '';
+
+while (1) {
+    # Read 1 byte
+    my $success = read $fh, my $byte, 1;
+
+    if (not defined $success) {
+        # Explode on error.
+        die $!
+    } elsif (not $success) {
+        # Exit the loop if no bytes were read.
+        last;
+    } else {
+        if (length($bitcode) > 0) {
+            $bitcode .= ', ';
+        }
+
+        # Print the numeric representation of the byte
+        $bitcode .= ord($byte);
+    }
+}
+close $fh;
+
+print "$before_bitcode$bitcode$after_bitcode\n";
diff --git a/compiler/builtins/bitcode/src/lib.rs b/compiler/builtins/bitcode/src/lib.rs
new file mode 100644
index 0000000000..52a6f2d8e0
--- /dev/null
+++ b/compiler/builtins/bitcode/src/lib.rs
@@ -0,0 +1,4 @@
+#[no_mangle]
+pub fn i64_to_f64_(num: i64) -> f64 {
+    num as f64
+}