Add instructions for generating boot images for local Compiler Explorer.

Also, update the instructions to build Compiler Explorer only once.

Bug: 330519779
Test: Follow the instructions.
Change-Id: I9ca1a7de1b81237ff78faff73a277e5504f580a4

2 files changed, 53 insertions, 7 deletions

diff --git a/test/generate-boot-image/generate-boot-image.cc b/test/generate-boot-image/generate-boot-image.cc
index 671aa379f1..3cd992f0c6 100644
--- a/test/generate-boot-image/generate-boot-image.cc
+++ b/test/generate-boot-image/generate-boot-image.cc
@@ -20,6 +20,7 @@
 #include <algorithm>
 #include <cstdlib>
 #include <iostream>
+#include <iterator>
 #include <string>
 #include <vector>
 
@@ -50,7 +51,7 @@ using ::art::testing::GetLibCoreDexLocations;
 constexpr const char* kUsage = R"(
 A commandline tool to generate a primary boot image for testing.
 
-Usage: generate-boot-image --output-dir=OUTPUT_DIR [OPTIONS]...
+Usage: generate-boot-image --output-dir=OUTPUT_DIR [OPTIONS]... [-- [DEX2OAT_OPTIONS]...]
 
 Supported options:
   --help: Print this text.
@@ -79,6 +80,7 @@ Supported options:
       host. The default on target is based on the ISA of this binary.
   --core-only=true|false: If true, only compile ART jars. Otherwise, also compile core-icu4j and
       conscrypt. Default: false
+  --: Arguments following '--' are directly passed to dex2oat.
 )";
 
 struct Options {
@@ -92,6 +94,7 @@ struct Options {
   std::string profile_file = "";
   std::string instruction_set = "";
   bool core_only = false;
+  std::vector<std::string> dex2oat_options;
 };
 
 [[noreturn]] void Usage(const std::string& message) {
@@ -162,6 +165,9 @@ int GenerateBootImage(const Options& options) {
   args.push_back(StringPrintf("--image=%s/boot.art", path.c_str()));
   args.push_back(StringPrintf("--oat-file=%s/boot.oat", path.c_str()));
 
+  std::move(
+      options.dex2oat_options.begin(), options.dex2oat_options.end(), std::back_inserter(args));
+
   int exit_code = system(BuildCommand(args).c_str());
   if (exit_code != 0) {
     LOG(ERROR) << "dex2oat invocation failed. Exit code: " << exit_code;
@@ -203,6 +209,10 @@ int Main(int argc, char** argv) {
         Usage(ART_FORMAT("Unrecognized --core-only value: '{}'", arg));
       }
       options.core_only = result == ParseBoolResult::kTrue;
+    } else if (arg == "--") {
+      for (i++; i < argc; i++) {
+        options.dex2oat_options.push_back(argv[i]);
+      }
     } else {
       Usage(ART_FORMAT("Unrecognized argument: '{}'", argv[i]));
     }
diff --git a/tools/compiler-explorer/compiler-explorer.md b/tools/compiler-explorer/compiler-explorer.md
index ff05487575..95866c14ea 100644
--- a/tools/compiler-explorer/compiler-explorer.md
+++ b/tools/compiler-explorer/compiler-explorer.md
@@ -39,8 +39,8 @@ This doc describes how to run a local instance of Compiler Explorer
     lunch aosp_cf_x86_64_phone-trunk_staging-userdebug
     ```
 
-    Note: You may use a different `lunch` target, as long as it can build the host binaries in the
-    later steps.
+    Note: You may use a different `lunch` target, as long as it can build the
+    host binaries in the later steps.
 
 1. Configure Compiler Explorer.
 
@@ -51,6 +51,12 @@ This doc describes how to run a local instance of Compiler Explorer
       xargs sed -i 's?{{compilersDir}}?'$COMPILER_EXPLORER_DIR/compilers'?'
     ```
 
+1. Build Compiler Explorer.
+
+    ```
+    (cd $COMPILER_EXPLORER_DIR/compiler-explorer && make prebuild)
+    ```
+
 1. Build and copy compilers except dex2oat.
 
     ```
@@ -80,14 +86,44 @@ This doc describes how to run a local instance of Compiler Explorer
     Note: You may choose to do this on `master-art` instead of on a full Android
     source tree if you wish.
 
+1. Generate boot images (optional but recommended).
+
+    ```
+    declare -a instruction_sets=("arm" "arm64" "x86" "x86_64" "riscv64")
+    m generate-boot-image
+    rm -rf $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app
+    mkdir -p $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app/apex/com.android.art/javalib
+    cp $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/bootjars/* \
+        $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app/apex/com.android.art/javalib
+    mkdir -p $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app/system/framework
+    for instruction_set in "${instruction_sets[@]}"; do
+      $ANDROID_HOST_OUT/bin/generate-boot-image64 \
+          --output-dir=$COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app/system/framework \
+          --compiler-filter=speed \
+          --use-profile=false \
+          --dex2oat-bin=$COMPILER_EXPLORER_DIR/compilers/dex2oat-local/x86_64/bin/dex2oat64 \
+          --android-root=$COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app \
+          --core-only=true \
+          --instruction-set=$instruction_set \
+          -- \
+          --runtime-arg \
+          -Xgc:CMC
+    done
+    ```
+
+    Note: You may change `instruction_sets` on the first line to only include
+    the instruction sets that you need, to speed up boot image generation.
+
+    Note: Although this step is not required, having boot images makes dex2oat generate better code.
+
 1. Start Compiler Explorer server.
 
     ```
-    (cd $COMPILER_EXPLORER_DIR/compiler-explorer && make)
+    (cd $COMPILER_EXPLORER_DIR/compiler-explorer && make run-only)
     ```
 
-    This may take a while. Once you see `Listening on http://localhost:10240/`,
-    you can open a browser with that address to access Compiler Explorer.
+    Once you see `Listening on http://localhost:10240/`, you can open a browser
+    with that address to access Compiler Explorer.
 
 When you iterate, press `Ctrl+C` to stop the server, and then repeat the last
-two steps.
+three steps.