From b33e4642724b2fd375a41fc8eca9a47e7075f093 Mon Sep 17 00:00:00 2001
From: Kevin Lubick <kjlubick@google.com>
Date: Tue, 25 Apr 2023 15:11:49 -0400
Subject: [PATCH] Enable trivial ABI for CanvasKit and Bazel build

This is a follow-up to http://review.skia.org/633089

This introduces a custom platform constraint which one could
use in a platform definition. This also lets us opt-in to it
in WASM builds (since I believe those don't care about ABI
compatibility).

Change-Id: I68c498d03726e82bd62f84581be14ea12bba3f2d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/678276
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
---
 bazel/platform/BUILD.bazel   | 12 ++++++++++++
 defines.bzl                  |  4 ++++
 modules/canvaskit/compile.sh |  1 +
 modules/pathkit/compile.sh   |  2 ++
 4 files changed, 19 insertions(+)

diff --git a/bazel/platform/BUILD.bazel b/bazel/platform/BUILD.bazel
index 3cd12b59963c..978c08b41037 100644
--- a/bazel/platform/BUILD.bazel
+++ b/bazel/platform/BUILD.bazel
@@ -80,3 +80,15 @@ constraint_value(
     constraint_setting = ":skia_hermetic_toolchain",
     visibility = ["//visibility:public"],
 )
+
+# This constraint allows us to have clang use a "trivial_abi" that saves code size but
+# breaks clients that aren't expecting it.
+# http://review.skia.org/633089
+# https://quuxplusone.github.io/blog/2018/05/02/trivial-abi-101/
+constraint_setting(name = "clang_abi_mode")
+
+constraint_value(
+    name = "trivial_abi",
+    constraint_setting = ":clang_abi_mode",
+    visibility = ["//visibility:public"],
+)
diff --git a/defines.bzl b/defines.bzl
index 7b0ee4f63634..3b9beae6a9d1 100644
--- a/defines.bzl
+++ b/defines.bzl
@@ -127,6 +127,10 @@ PLATFORM_DEFINES = select({
         "SK_FORCE_AAA",
     ],
     "//conditions:default": [],
+}) + select({
+    "//bazel/platform:trivial_abi": ["SK_TRIVIAL_ABI=[[clang::trivial_abi]]"],
+    "//bazel/common_config_settings:cpu_wasm": ["SK_TRIVIAL_ABI=[[clang::trivial_abi]]"],
+    "//conditions:default": [],
 })
 
 # Skia's public headers can work with any version of a Vulkan header. When compiling Skia internals,
diff --git a/modules/canvaskit/compile.sh b/modules/canvaskit/compile.sh
index df3cb42b5a3b..f9d8ecb6781b 100755
--- a/modules/canvaskit/compile.sh
+++ b/modules/canvaskit/compile.sh
@@ -208,6 +208,7 @@ echo "Compiling"
   --args="is_debug=${IS_DEBUG} \
   is_official_build=${IS_OFFICIAL_BUILD} \
   is_component_build=false \
+  is_trivial_abi=true \
   werror=true \
   target_cpu=\"wasm\" \
   \
diff --git a/modules/pathkit/compile.sh b/modules/pathkit/compile.sh
index 5f029ad928f6..d4f90ed40002 100755
--- a/modules/pathkit/compile.sh
+++ b/modules/pathkit/compile.sh
@@ -89,6 +89,7 @@ echo "Compiling bitcode"
   ] \
   is_debug=false \
   is_official_build=true \
+  is_trivial_abi=true \
   is_component_build=false \
   werror=true \
   target_cpu=\"wasm\" "
@@ -104,6 +105,7 @@ ${EMCXX} $RELEASE_CONF -std=c++17 \
 --pre-js $BASE_DIR/helper.js \
 --pre-js $BASE_DIR/chaining.js \
 -fno-rtti -fno-exceptions -DEMSCRIPTEN_HAS_UNBOUND_TYPE_NAMES=0 \
+"-DSK_TRIVIAL_ABI=[[clang::trivial_abi]]" \
 $WASM_CONF \
 -sERROR_ON_UNDEFINED_SYMBOLS=1 \
 -sEXPORT_NAME="PathKitInit" \