From 41abb0b9708a4a929708b6073de0eefce79462ca Mon Sep 17 00:00:00 2001
From: Michael Bestas <mkbestas@lineageos.org>
Date: Mon, 14 Nov 2022 13:09:00 +0200
Subject: [PATCH] kernel: Allow devices to opt-in for full LLVM build

android11-5.4 kernel can fully compile with LLVM with a few cherrypicks
from android12-5.4 and android12-5.10

Change-Id: Ib71935d284ad78f1c23d039c15bfc5e0314a19eb
---
 build/tasks/kernel.mk       |  9 +++------
 config/BoardConfigKernel.mk | 14 ++++++++++++--
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/build/tasks/kernel.mk b/build/tasks/kernel.mk
index 4bdcbcb2..2409894a 100644
--- a/build/tasks/kernel.mk
+++ b/build/tasks/kernel.mk
@@ -227,7 +227,7 @@ ifeq ($(or $(FULL_RECOVERY_KERNEL_BUILD), $(FULL_KERNEL_BUILD)),true)
 # Add host bin out dir to path
 PATH_OVERRIDE := PATH=$(KERNEL_BUILD_OUT_PREFIX)$(HOST_OUT_EXECUTABLES):$$PATH
 ifneq ($(TARGET_KERNEL_CLANG_COMPILE),false)
-    ifeq (,$(filter 5.10, $(TARGET_KERNEL_VERSION)))
+    ifneq ($(KERNEL_NO_GCC), true)
         ifeq ($(KERNEL_ARCH),arm64)
             KERNEL_CLANG_TRIPLE ?= CLANG_TRIPLE=aarch64-linux-gnu-
         else ifeq ($(KERNEL_ARCH),arm)
@@ -243,11 +243,8 @@ ifneq ($(TARGET_KERNEL_CLANG_COMPILE),false)
     endif
 endif
 
-ifeq ($(TARGET_KERNEL_LLVM_BINUTILS), false)
-    # 5.10+ can fully compile without gcc
-    ifeq (,$(filter 5.10, $(TARGET_KERNEL_VERSION)))
-        PATH_OVERRIDE += PATH=$(KERNEL_TOOLCHAIN_PATH_gcc):$$PATH
-    endif
+ifneq ($(KERNEL_NO_GCC), true)
+    PATH_OVERRIDE += PATH=$(KERNEL_TOOLCHAIN_PATH_gcc):$$PATH
 endif
 
 # System tools are no longer allowed on 10+
diff --git a/config/BoardConfigKernel.mk b/config/BoardConfigKernel.mk
index d60297ec..19e55746 100644
--- a/config/BoardConfigKernel.mk
+++ b/config/BoardConfigKernel.mk
@@ -31,6 +31,8 @@
 #   TARGET_KERNEL_CLANG_PATH           = Clang prebuilts path, optional
 #
 #   TARGET_KERNEL_LLVM_BINUTILS        = Use LLVM binutils, defaults to true
+#   TARGET_KERNEL_NO_GCC               = Fully compile the kernel without GCC.
+#                                        Defaults to false
 #   TARGET_KERNEL_VERSION              = Reported kernel version in top level kernel
 #                                        makefile. Can be overriden in device trees
 #                                        in the event of prebuilt kernel.
@@ -71,6 +73,15 @@ KERNEL_VERSION := $(shell grep -s "^VERSION = " $(TARGET_KERNEL_SOURCE)/Makefile
 KERNEL_PATCHLEVEL := $(shell grep -s "^PATCHLEVEL = " $(TARGET_KERNEL_SOURCE)/Makefile | awk '{ print $$3 }')
 TARGET_KERNEL_VERSION ?= $(shell echo $(KERNEL_VERSION)"."$(KERNEL_PATCHLEVEL))
 
+# 5.10+ can fully compile without GCC by default
+ifneq (,$(filter 5.10, $(TARGET_KERNEL_VERSION)))
+    TARGET_KERNEL_NO_GCC ?= true
+endif
+
+ifeq ($(TARGET_KERNEL_NO_GCC), true)
+    KERNEL_NO_GCC := true
+endif
+
 ifneq ($(TARGET_KERNEL_CLANG_VERSION),)
     KERNEL_CLANG_VERSION := clang-$(TARGET_KERNEL_CLANG_VERSION)
 else
@@ -95,8 +106,7 @@ KERNEL_MAKE_FLAGS += -j$(shell getconf _NPROCESSORS_ONLN)
 TOOLS_PATH_OVERRIDE := \
     PERL5LIB=$(BUILD_TOP)/prebuilts/tools-lineage/common/perl-base
 
-# 5.10+ can fully compile without gcc
-ifeq (,$(filter 5.10, $(TARGET_KERNEL_VERSION)))
+ifneq ($(KERNEL_NO_GCC), true)
     GCC_PREBUILTS := $(BUILD_TOP)/prebuilts/gcc/$(HOST_PREBUILT_TAG)
     # arm64 toolchain
     KERNEL_TOOLCHAIN_arm64 := $(GCC_PREBUILTS)/aarch64/aarch64-linux-android-4.9/bin