Cross-compilation error when using -march=rv64gcv

[moluopro]

When cross-compiling the riscv64 platform, an error was encountered because the compilation parameter “-march=rv64gcv“ was specified. This parameter is necessary as I am doing related optimizations.

Why is it that when compiling with riscv64-linux-gnu-g++ there are still parts of the code that use the x86 compiler?

How can I specify compilation parameters for both compilers separately? Please let me know the specifics of the configuration file I want to modify. Thanks!

System version: Ubuntu24 LTS
Dart version: latest code in main branch

moluo@ubuntu:~/work/dart-sdk/sdk$ ./tools/build.py --no-clang --mode release --arch riscv64 create_sdk
Done. Made 665 targets from 129 files in 170ms
buildtools/ninja/ninja -C out/ReleaseXRISCV64 create_sdk
ninja: Entering directory `out/ReleaseXRISCV64'
[1188/4082] CXX obj/third_party/icu/source/i18n/icui18n.formattedvalue.o
../../third_party/icu/source/i18n/formattedvalue.cpp: In function ‘const char16_t* icu_74::ufmtval_getString_74(const UFormattedValue*, int32_t*, UErrorCode*)’:
../../third_party/icu/source/i18n/formattedvalue.cpp:215:1: warning: function may return address of local variable [-Wreturn-local-addr]
  215 | }
      | ^
../../third_party/icu/source/i18n/formattedvalue.cpp:205:19: note: declared here
  205 |     UnicodeString readOnlyAlias = impl->fFormattedValue->toTempString(*ec);
      |                   ^~~~~~~~~~~~~
[1194/4082] CXX obj/third_party/icu/source/i18n/icui18n.decNumber.o
../../third_party/icu/source/i18n/decNumber.cpp: In function ‘decNumber* uprv_decNumberLog10_74(decNumber*, const decNumber*, decContext*)’:
../../third_party/icu/source/i18n/decNumber.cpp:1528:14: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 1528 |     w->lsu[1]=1; w->lsu[0]=0;           /* ..  */
      |     ~~~~~~~~~^~
In file included from ../../third_party/icu/source/i18n/decNumber.cpp:184:
../../third_party/icu/source/i18n/decNumber.h:89:19: note: at offset 1 into destination object ‘decNumber::lsu’ of size 1
   89 |     decNumberUnit lsu[DECNUMUNITS];
      |                   ^~~
../../third_party/icu/source/i18n/decNumber.cpp:1528:14: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 1528 |     w->lsu[1]=1; w->lsu[0]=0;           /* ..  */
      |     ~~~~~~~~~^~
../../third_party/icu/source/i18n/decNumber.h:89:19: note: at offset 1 into destination object ‘decNumber::lsu’ of size 1
   89 |     decNumberUnit lsu[DECNUMUNITS];
      |                   ^~~
../../third_party/icu/source/i18n/decNumber.cpp: In function ‘decNumber* uprv_decNumberSquareRoot_74(decNumber*, const decNumber*, decContext*)’:
../../third_party/icu/source/i18n/decNumber.cpp:2974:31: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 2974 |         t->lsu[0]=9; t->lsu[1]=5; t->lsu[2]=2;
      |                      ~~~~~~~~~^~
../../third_party/icu/source/i18n/decNumber.h:89:19: note: at offset 1 into destination object ‘decNumber::lsu’ of size 1
   89 |     decNumberUnit lsu[DECNUMUNITS];
      |                   ^~~
../../third_party/icu/source/i18n/decNumber.cpp:2974:44: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
 2974 |         t->lsu[0]=9; t->lsu[1]=5; t->lsu[2]=2;
      |                                   ~~~~~~~~~^~
../../third_party/icu/source/i18n/decNumber.h:89:19: note: at offset 2 into destination object ‘decNumber::lsu’ of size 1
   89 |     decNumberUnit lsu[DECNUMUNITS];
      |                   ^~~
[2534/4082] CXX x64/obj/runtime/bin/gen_snapshot_dart_io.console_win.o
FAILED: x64/obj/runtime/bin/gen_snapshot_dart_io.console_win.o 
x86_64-linux-gnu-g++ -MMD -MF x64/obj/runtime/bin/gen_snapshot_dart_io.console_win.o.d -DDART_IO_SECURE_SOCKET_DISABLED -D_FORTIFY_SOURCE=2 -DNDEBUG -DSUPPORT_PERFETTO -DDART_PRECOMPILER -DTARGET_ARCH_RISCV64 -DDART_TARGET_OS_LINUX -I../../runtime -I../../third_party -I../.. -Ix64/gen -I../../runtime/include -I../../third_party/zlib -m64 -march=x86-64 -msse2 -fPIE -Wall -Wextra -Werror -Wendif-labels -Wno-missing-field-initializers -Wno-unused-parameter -Wno-ignored-qualifiers -fdebug-prefix-map=/home/moluo/work/dart-sdk/sdk/= -no-canonical-prefixes -fvisibility=hidden -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -march=rv64gcv -O2 -fno-ident -fdata-sections -ffunction-sections -g3 -ggdb3 -Wno-unused-parameter -Wno-unused-private-field -Wnon-virtual-dtor -Wvla -Woverloaded-virtual -Wno-comments -g3 -ggdb3 -fno-rtti -fno-exceptions -Wno-cast-function-type -Wno-dangling-reference -O2 -fvisibility-inlines-hidden -fno-omit-frame-pointer -std=c++20 -std=c++20 -fno-rtti -c ../../runtime/bin/console_win.cc -o x64/obj/runtime/bin/gen_snapshot_dart_io.console_win.o
cc1plus: error: bad value ‘rv64gcv’ for ‘-march=’ switch
cc1plus: note: valid arguments to ‘-march=’ switch are: nocona core2 nehalem corei7 westmere sandybridge corei7-avx ivybridge core-avx-i haswell core-avx2 broadwell skylake skylake-avx512 cannonlake icelake-client rocketlake icelake-server cascadelake tigerlake cooperlake sapphirerapids emeraldrapids alderlake raptorlake meteorlake graniterapids graniterapids-d bonnell atom silvermont slm goldmont goldmont-plus tremont gracemont sierraforest grandridge knl knm x86-64 x86-64-v2 x86-64-v3 x86-64-v4 eden-x2 nano nano-1000 nano-2000 nano-3000 nano-x2 eden-x4 nano-x4 lujiazui k8 k8-sse3 opteron opteron-sse3 athlon64 athlon64-sse3 athlon-fx amdfam10 barcelona bdver1 bdver2 bdver3 bdver4 znver1 znver2 znver3 znver4 btver1 btver2 native
cc1plus: note: unrecognized command-line option ‘-Wno-unused-private-field’ may have been intended to silence earlier diagnostics
[2535/4082] CXX x64/obj/runtime/bin/gen_snapshot_dart_io.console_posix.o
FAILED: x64/obj/runtime/bin/gen_snapshot_dart_io.console_posix.o 
x86_64-linux-gnu-g++ -MMD -MF x64/obj/runtime/bin/gen_snapshot_dart_io.console_posix.o.d -DDART_IO_SECURE_SOCKET_DISABLED -D_FORTIFY_SOURCE=2 -DNDEBUG -DSUPPORT_PERFETTO -DDART_PRECOMPILER -DTARGET_ARCH_RISCV64 -DDART_TARGET_OS_LINUX -I../../runtime -I../../third_party -I../.. -Ix64/gen -I../../runtime/include -I../../third_party/zlib -m64 -march=x86-64 -msse2 -fPIE -Wall -Wextra -Werror -Wendif-labels -Wno-missing-field-initializers -Wno-unused-parameter -Wno-ignored-qualifiers -fdebug-prefix-map=/home/moluo/work/dart-sdk/sdk/= -no-canonical-prefixes -fvisibility=hidden -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -march=rv64gcv -O2 -fno-ident -fdata-sections -ffunction-sections -g3 -ggdb3 -Wno-unused-parameter -Wno-unused-private-field -Wnon-virtual-dtor -Wvla -Woverloaded-virtual -Wno-comments -g3 -ggdb3 -fno-rtti -fno-exceptions -Wno-cast-function-type -Wno-dangling-reference -O2 -fvisibility-inlines-hidden -fno-omit-frame-pointer -std=c++20 -std=c++20 -fno-rtti -c ../../runtime/bin/console_posix.cc -o x64/obj/runtime/bin/gen_snapshot_dart_io.console_posix.o
cc1plus: error: bad value ‘rv64gcv’ for ‘-march=’ switch
cc1plus: note: valid arguments to ‘-march=’ switch are: nocona core2 nehalem corei7 westmere sandybridge corei7-avx ivybridge core-avx-i haswell core-avx2 broadwell skylake skylake-avx512 cannonlake icelake-client rocketlake icelake-server cascadelake tigerlake cooperlake sapphirerapids emeraldrapids alderlake raptorlake meteorlake graniterapids graniterapids-d bonnell atom silvermont slm goldmont goldmont-plus tremont gracemont sierraforest grandridge knl knm x86-64 x86-64-v2 x86-64-v3 x86-64-v4 eden-x2 nano nano-1000 nano-2000 nano-3000 nano-x2 eden-x4 nano-x4 lujiazui k8 k8-sse3 opteron opteron-sse3 athlon64 athlon64-sse3 athlon-fx amdfam10 barcelona bdver1 bdver2 bdver3 bdver4 znver1 znver2 znver3 znver4 btver1 btver2 native
cc1plus: note: unrecognized command-line option ‘-Wno-unused-private-field’ may have been intended to silence earlier diagnostics
[2551/4082] ACTION //utils/dart2wasm:compile_dart2wasm_platform(//build/toolchain/linux:riscv64)
ninja: build stopped: subcommand failed.
BUILD FAILED

The reason for the error is here:

FAILED: x64/obj/runtime/bin/gen_snapshot_dart_io.console_win.o
x86_64-linux-gnu-g++ -MMD -MF x64/obj/runtime/bin/gen_snapshot_dart_io.console_win.o.d

[moluopro]

I just modified it here and encountered the error:

[rmacnak-google]

The Dart build involves compiling some binaries that will run on the host during the build. To set flags for the target toolchain and not the host toolchain, you need something like

if (current_cpu == "riscv64") {
  cflags += [ "-march=rv64gcv "]
}

probably in config("compiler") in //build/config/compiler/BUILD.gn

[moluopro]

Thank you very much!