Refactor three_billion_instructions into library

Summary: Want to use it in a test for code to measure current thread instruction counts.

Reviewed By: krallin

Differential Revision: D54375084

fbshipit-source-id: 0dc23a11e94136604c23541352a93dcd6bf28172

app/buck2_miniperf/BUCK

@@ -46,6 +46,6 @@ rust_library(
     }),
     test_env = {
         "MINIPERF": "$(exe_target :buck2_miniperf)",
-        "THREE_BILLION_INSTRUCTIONS": "$(exe_target //buck2/shed/three_billion_instructions:three_billion_instructions)",
+        "THREE_BILLION_INSTRUCTIONS": "$(exe_target //buck2/shed/three_billion_instructions:three_billion_instructions-bin)",
     },
 )

shed/three_billion_instructions/BUCK

@@ -1,11 +1,21 @@
 load("@fbcode_macros//build_defs:rust_binary.bzl", "rust_binary")
+load("@fbcode_macros//build_defs:rust_library.bzl", "rust_library")
 load("@fbsource//tools/build_defs:glob_defs.bzl", "glob")
 
 oncall("build_infra")
 
-rust_binary(
+rust_library(
     name = "three_billion_instructions",
     srcs = glob(
         ["src/**/*.rs"],
     ),
 )
+
+rust_binary(
+    name = "three_billion_instructions-bin",
+    srcs = ["bin/three_billion_instructions.rs"],
+    crate_root = "bin/three_billion_instructions.rs",
+    deps = [
+        ":three_billion_instructions",
+    ],
+)

shed/three_billion_instructions/bin/three_billion_instructions.rs

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under both the MIT license found in the
+ * LICENSE-MIT file in the root directory of this source tree and the Apache
+ * License, Version 2.0 found in the LICENSE-APACHE file in the root directory
+ * of this source tree.
+ */
+
+use three_billion_instructions::three_billion_instructions;
+
+/// Run 3B instructions.
+fn main() {
+    three_billion_instructions();
+}

shed/three_billion_instructions/src/main.rs → shed/three_billion_instructions/src/lib.rs

@@ -8,28 +8,28 @@
  */
 
 /// Run 3B instructions.
-fn main() {
+pub fn three_billion_instructions() {
     let mut x = 1_000_000_000u64;
 
     #[cfg(target_arch = "x86_64")]
     unsafe {
         std::arch::asm!(
-            "2:",
-            "sub {0:r}, 1",
-            "cmp {0:r}, 0",
-            "jne 2b",
-            inout(reg) x,
+        "2:",
+        "sub {0:r}, 1",
+        "cmp {0:r}, 0",
+        "jne 2b",
+        inout(reg) x,
         );
     }
 
     #[cfg(target_arch = "aarch64")]
     unsafe {
         std::arch::asm!(
-            "2:",
-            "sub {0:x}, {0:x}, 1",
-            "cmp {0:x}, 0",
-            "bne 2b",
-            inout(reg) x,
+        "2:",
+        "sub {0:x}, {0:x}, 1",
+        "cmp {0:x}, 0",
+        "bne 2b",
+        inout(reg) x,
         );
     }