[wasm-split] Read and use profiles (#3400)

Read the profiles produced by wasm-split's instrumentation to guide splitting.
In this initial implementation, all functions that the profile shows to have
been called are kept in the initial module. In the future, users may be able to
tune this so that functions that are run later will still be split out.

2 files changed, 92 insertions, 0 deletions

diff --git a/test/lit/wasm-split/call_exports.mjs b/test/lit/wasm-split/call_exports.mjs
new file mode 100644
index 000000000..546564d2e
--- /dev/null
+++ b/test/lit/wasm-split/call_exports.mjs
@@ -0,0 +1,25 @@
+// Instantiates an instrumented module, calls the given exports, then collects
+// its wasm-split profile and writes it to a given file.
+//
+// Usage:
+//
+//  node call_exports.mjs <module> <profile> <export>*
+
+import * as fs from 'fs';
+
+let wasm = process.argv[2];
+let outFile = process.argv[3];
+
+// Create the Wasm instance
+let { _, instance } = await WebAssembly.instantiate(fs.readFileSync(wasm));
+
+// Call the specified exports
+for (let i = 4; i < process.argv.length; i++) {
+  console.log('calling', process.argv[i]);
+  instance.exports[process.argv[i]]();
+}
+
+// Create and read the profile
+let profileSize = instance.exports['__write_profile'](0, 2**32 - 1);
+let profileData = Buffer.from(instance.exports.memory.buffer, 0, profileSize);
+fs.writeFileSync(outFile, profileData);
diff --git a/test/lit/wasm-split/profile-guided.wast b/test/lit/wasm-split/profile-guided.wast
new file mode 100644
index 000000000..f2d79f99c
--- /dev/null
+++ b/test/lit/wasm-split/profile-guided.wast
@@ -0,0 +1,67 @@
+;; Instrument the binary
+
+;; RUN: wasm-split --instrument %s -o %t.instrumented.wasm
+
+;; Create profiles
+
+;; RUN: node %S/call_exports.mjs %t.instrumented.wasm %t.foo.prof foo
+;; RUN: node %S/call_exports.mjs %t.instrumented.wasm %t.bar.prof bar
+;; RUN: node %S/call_exports.mjs %t.instrumented.wasm %t.both.prof foo bar
+;; RUN: node %S/call_exports.mjs %t.instrumented.wasm %t.none.prof
+
+;; Create profile-guided splits
+
+;; RUN: wasm-split %s --profile=%t.foo.prof -v -o1 %t.foo.1.wasm -o2 %t.foo.2.wasm \
+;; RUN:   | filecheck %s --check-prefix FOO
+
+;; FOO: Keeping functions: deep_foo_callee, foo, foo_callee, shared_callee
+;; FOO: Splitting out functions: bar, bar_callee, uncalled
+
+;; RUN: wasm-split %s --profile=%t.bar.prof -v -o1 %t.bar.1.wasm -o2 %t.bar.2.wasm \
+;; RUN:   | filecheck %s --check-prefix BAR
+
+;; BAR: Keeping functions: bar, bar_callee, shared_callee
+;; BAR: Splitting out functions: deep_foo_callee, foo, foo_callee, uncalled
+
+;; RUN: wasm-split %s --profile=%t.both.prof -v -o1 %t.both.1.wasm -o2 %t.both.2.wasm \
+;; RUN:   | filecheck %s --check-prefix BOTH
+
+;; BOTH: Keeping functions: bar, bar_callee, deep_foo_callee, foo, foo_callee, shared_callee
+;; BOTH: Splitting out functions: uncalled
+
+;; RUN: wasm-split %s --profile=%t.none.prof -v -o1 %t.none.1.wasm -o2 %t.none.2.wasm \
+;; RUN:   | filecheck %s --check-prefix NONE
+
+;; NONE: Keeping functions:
+;; NONE: Splitting out functions: bar, bar_callee, deep_foo_callee, foo, foo_callee, shared_callee, uncalled
+
+
+(module
+  (memory $mem 1 1)
+  (export "memory" (memory $mem))
+  (export "foo" (func $foo))
+  (export "bar" (func $bar))
+  (export "uncalled" (func $uncalled))
+
+  (func $foo
+    (call $foo_callee)
+    (call $shared_callee)
+  )
+
+  (func $bar
+    (call $shared_callee)
+    (call $bar_callee)
+  )
+
+  (func $uncalled)
+
+  (func $foo_callee
+    (call $deep_foo_callee)
+  )
+
+  (func $bar_callee)
+
+  (func $shared_callee)
+
+  (func $deep_foo_callee)
+)