Engine build failure targeting armv6

[jwinarske]

Has armv6 been deprecated? The target is Raspberry Pi 0-W ($10) w/LCD hat.

In file included from ../../third_party/dart/runtime/vm/thread_interrupter_linux.cc:12:
In file included from ../../third_party/dart/runtime/vm/profiler.h:19:
In file included from ../../third_party/dart/runtime/vm/thread_interrupter.h:10:
../../third_party/dart/runtime/vm/signal_handler.h:99:18: error: inline asm clobber list contains reserved registers: R11, SP [-Werror,-Winline-asm]
    asm volatile("nop; nop; nop; nop;"
                 ^
<inline asm>:1:1: note: instantiated into assembly here
        nop; nop; nop; nop;
^
../../third_party/dart/runtime/vm/signal_handler.h:99:18: note: Reserved registers on the clobber list may not be preserved across the asm statement, and clobbering them may lead to undefined behaviour.
    asm volatile("nop; nop; nop; nop;"
                 ^
<inline asm>:1:1: note: instantiated into assembly here
        nop; nop; nop; nop;
^
1 error generated.

Steps to Reproduce

Clang8 Toolchain with default triple of arm-linux-gnueabi

./flutter/tools/gn --runtime-mode debug --embedder-for-target --full-dart-sdk --enable-fontconfig --target-os linux --linux-cpu arm --arm-float-abi hard --target-triple arm-linux-gnueabihf --target-sysroot /media/joel/SolidState/rpi/rpi0w/tmp/work/arm1176jzfshf-vfp-poky-linux-gnueabi/flutter-engine/git-r0/recipe-sysroot --target-toolchain /media/joel/SolidState/LLVM8.0

Post Config:

append to args file

arm_float_abi = "hard"
arm_tune = "arm1176jzf-s"

Then

diff --git a/build/config/arm.gni b/build/config/arm.gni
index 7a293e6..1ce6f39 100644
--- a/build/config/arm.gni
+++ b/build/config/arm.gni
@@ -7,7 +7,7 @@ if (current_cpu == "arm" || current_cpu == "arm64") {
     # Version of the ARM processor when compiling on ARM. Ignored on non-ARM
     # platforms.
     if (current_cpu == "arm") {
-      arm_version = 7
+      arm_version = 6
     } else if(current_cpu == "arm64") {
       arm_version = 8
     } else {
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 294843d..8310bab 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -635,14 +635,14 @@ if (is_win) {
 
   if (!use_xcode) {
     default_warning_flags += [
-      "-Wno-implicit-int-float-conversion",
-      "-Wno-c99-designator",
+#      "-Wno-implicit-int-float-conversion",
+#      "-Wno-c99-designator",
     ]
     if (!is_fuchsia) {
       default_warning_flags += [
-        "-Wno-non-c-typedef-for-linkage",
-        "-Wno-deprecated-copy",
-        "-Wno-range-loop-construct",
+#        "-Wno-non-c-typedef-for-linkage",
+#        "-Wno-deprecated-copy",
+#        "-Wno-range-loop-construct",
       ]
     }
   }

[TahaTesser]

Hi @jwinarske
can you please provide your `flutter doctor -v'?

[jwinarske]

git log -1
commit 3a27de1

[jwinarske]

Given I'm using a current Kernel, I'm figuring this is safe

diff --git a/runtime/vm/signal_handler.h b/runtime/vm/signal_handler.h
index 41eea90dc5..4ff27f91b7 100644
--- a/runtime/vm/signal_handler.h
+++ b/runtime/vm/signal_handler.h
@@ -44,7 +44,7 @@ struct sigset_t {};
 #if defined(HOST_ARCH_ARM) &&                                                  \
     (defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)) &&                    \
     !defined(__thumb__)
-#define USE_SIGNAL_HANDLER_TRAMPOLINE
+//#define USE_SIGNAL_HANDLER_TRAMPOLINE
 #endif
 
 namespace dart {

[jwinarske]

src/third_party/libpng/arm/filter_neon.S is hard coded for armv-a and neon

FAILED: obj/third_party/libpng/arm/libpng.filter_neon.o 
/media/joel/SolidState/LLVM8.0/bin/clang -MD -MF obj/third_party/libpng/arm/libpng.filter_neon.o.d --target=arm-linux-gnueabihf --sysroot /media/joel/SolidState/rpi/rpi0w/tmp/work/arm1176jzfshf-vfp-poky-linux-gnueabi/flutter-engine/git-r0/recipe-sysroot -DPNG_ARM_NEON_OPT=2 -DUSE_OPENSSL=1 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_LIBCPP_DISABLE_AVAILABILITY=1 -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -I../.. -Igen -I../../third_party/libcxx/include -I../../third_party/libcxxabi/include -I../../third_party/libcxxabi/include -I../../third_party/libpng -I../../third_party/zlib -fno-strict-aliasing -fstack-protector --param=ssp-buffer-size=4 -march=armv6 -mfloat-abi=hard -fPIC -pipe -pthread -fcolor-diagnostics -fno-strict-aliasing -fstack-protector --param=ssp-buffer-size=4 -march=armv6 -mfloat-abi=hard -fPIC -pipe -pthread -fcolor-diagnostics -mfpu=vfp -Wall -Wextra -Wendif-labels -Werror -Wno-missing-field-initializers -Wno-unused-parameter -fvisibility=hidden --sysroot=/media/joel/SolidState/rpi/rpi0w/tmp/work/arm1176jzfshf-vfp-poky-linux-gnueabi/flutter-engine/git-r0/recipe-sysroot -Wstring-conversion -Wnewline-eof -O2 -fno-ident -fdata-sections -ffunction-sections -g0  -c ../../third_party/libpng/arm/filter_neon.S -o obj/third_party/libpng/arm/libpng.filter_neon.o
<instantiation>:18:9: error: unknown directive
        .func skia_png_read_filter_row_sub4_neon
        ^

Fix for armv6 (no-neon)

diff --git a/third_party/libpng/BUILD.gn b/third_party/libpng/BUILD.gn
index d67361c..4716b1e 100644
--- a/third_party/libpng/BUILD.gn
+++ b/third_party/libpng/BUILD.gn
@@ -48,7 +48,7 @@ source_set("libpng") {
       "arm/filter_neon_intrinsics.c",
     ]
 
-    defines += [ "PNG_ARM_NEON_OPT=2" ]
+    defines += [ "PNG_ARM_NEON_OPT=0" ]
   }
 
   deps = [

[jwinarske]

This one is interesting. The toolchain switches from my custom specified one to the host compiler

[809/1673] /media/joel/SolidState/LLVM8.0/bin/clang++ -MD -MF obj/third_party/skia/src/ports/typeface_freetype.SkFontHost_FreeType_common.o.d --target=arm-linux-gnueabihf --sysroot /media/joel/SolidState/rpi/rpi0w/tmp/work/arm1176jzfshf-vfp-poky-linux-gnueabi/flutter-engine/git-r0/recipe-sysroot -DUSE_OPENSSL=1 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_LIBCPP_DISABLE_AVAILABILITY=1 -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DSK_R32_SHIFT=16 -DSK_DISABLE_REDUCE_OPLIST_SPLITTING -DSK_ENABLE_DUMP_GPU -DSK_DISABLE_AAA -DSK_DISABLE_READBUFFER -DSK_DISABLE_EFFECT_DESERIALIZATION -DSK_SUPPORT_LEGACY_DIDCONCAT44 -DSK_DISABLE_LEGACY_SHADERCONTEXT -DSK_DISABLE_LOWP_RASTER_PIPELINE -DSK_FORCE_RASTER_PIPELINE_BLITTER -DSK_GL -DSK_GAMMA_APPLY_TO_A8 -DSKIA_IMPLEMENTATION=1 -I../.. -Igen -I../../third_party/libcxx/include -I../../third_party/libcxxabi/include -I../../third_party/libcxxabi/include -I../../third_party/skia -I../../third_party/freetype2/include -fno-strict-aliasing -fstack-protector --param=ssp-buffer-size=4 -march=armv6 -mfloat-abi=hard -fPIC -pipe -pthread -fcolor-diagnostics -mfpu=vfp -Wall -Wextra -Wendif-labels -Werror -Wno-missing-field-initializers -Wno-unused-parameter -fvisibility=hidden --sysroot=/media/joel/SolidState/rpi/rpi0w/tmp/work/arm1176jzfshf-vfp-poky-linux-gnueabi/flutter-engine/git-r0/recipe-sysroot -Wstring-conversion -Wnewline-eof -O2 -fno-ident -fdata-sections -ffunction-sections -g0 -Wno-unused-function -Wno-unused-variable -fvisibility-inlines-hidden -std=c++17 -fno-rtti -nostdinc++ -nostdinc++ -fno-exceptions -c ../../third_party/skia/src/ports/SkFontHost_FreeType_common.cpp -o obj/third_party/skia/src/ports/typeface_freetype.SkFontHost_FreeType_common.o
[810/1673] ../../buildtools/linux-x64/clang/bin/clang++ -MD -MF clang_x64/obj/third_party/dart/runtime/bin/gen_snapshot.snapshot_utils.o.d -DEXCLUDE_CFE_AND_KERNEL_PLATFORM -DUSE_OPENSSL=1 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_LIBCPP_DISABLE_AVAILABILITY=1 -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DNDEBUG -DDART_PRECOMPILER -DTARGET_ARCH_ARM -DTARGET_OS_LINUX -I../../third_party/dart/runtime -I../../third_party -I../.. -Iclang_x64/gen -I../../third_party/libcxx/include -I../../third_party/libcxxabi/include -I../../third_party/libcxxabi/include -I../../third_party/dart/runtime/include -I../../third_party/dart/runtime -I../../third_party/dart/runtime/include -fno-strict-aliasing -fstack-protector --param=ssp-buffer-size=4 -m64 -march=x86-64 -fPIC -pipe -pthread -fcolor-diagnostics -Wall -Wextra -Wendif-labels -Werror -Wno-missing-field-initializers -Wno-unused-parameter -fvisibility=hidden -Wstring-conversion -Wnewline-eof -O2 -fno-ident -fdata-sections -ffunction-sections -g0 -Werror -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field -Wnon-virtual-dtor -Wvla -Wno-conversion-null -Woverloaded-virtual -Wno-comments -g3 -ggdb3 -fno-rtti -fno-exceptions -Wimplicit-fallthrough -O3 -fvisibility-inlines-hidden -std=c++17 -fno-rtti -nostdinc++ -nostdinc++ -fno-exceptions   -c ../../third_party/dart/runtime/bin/snapshot_utils.cc -o clang_x64/obj/third_party/dart/runtime/bin/gen_snapshot.snapshot_utils.o

[jwinarske]

@mit-mit will Dart AOT compilation ever be supported on armv6?

#22380
https://github.com/dart-lang/sdk/wiki/Building-Dart-SDK-for-Raspberry-Pi-1

[iapicca]

HI @jwinarske
given this answer
in the issue you linked the armV&6 architecture isn't supported anymore,
the same issue is in fact a feature request to support said architecture

Please follow up on that issue,
I'm closing the current one as duplicate.
If you disagree please write in the comments
and I will reopen it.
Thank you

#22492
dart-lang/sdk#34874