diff --git a/src/secp256k1/ci/cirrus.sh b/src/secp256k1/ci/cirrus.sh
new file mode 100755
index 0000000000..8495c39203
--- /dev/null
+++ b/src/secp256k1/ci/cirrus.sh
@@ -0,0 +1,118 @@
+#!/bin/sh
+
+set -eux
+
+export LC_ALL=C
+
+# Print relevant CI environment to allow reproducing the job outside of CI.
+print_environment() {
+    # Turn off -x because it messes up the output
+    set +x
+    # There are many ways to print variable names and their content. This one
+    # does not rely on bash.
+    for var in WERROR_CFLAGS MAKEFLAGS BUILD \
+            ECMULTWINDOW ECMULTGENPRECISION ASM WIDEMUL WITH_VALGRIND EXTRAFLAGS \
+            EXPERIMENTAL ECDH RECOVERY SCHNORRSIG \
+            SECP256K1_TEST_ITERS BENCH SECP256K1_BENCH_ITERS CTIMETESTS\
+            EXAMPLES \
+            HOST WRAPPER_CMD \
+            CC CFLAGS CPPFLAGS AR NM
+    do
+        eval "isset=\${$var+x}"
+        if [ -n "$isset" ]; then
+            eval "val=\${$var}"
+            # shellcheck disable=SC2154
+            printf '%s="%s" ' "$var" "$val"
+        fi
+    done
+    echo "$0"
+    set -x
+}
+print_environment
+
+# Start persistent wineserver if necessary.
+# This speeds up jobs with many invocations of wine (e.g., ./configure with MSVC) tremendously.
+case "$WRAPPER_CMD" in
+    *wine*)
+        # Make sure to shutdown wineserver whenever we exit.
+        trap "wineserver -k || true" EXIT INT HUP
+        # This is apparently only reliable when we run a dummy command such as "hh.exe" afterwards.
+        wineserver -p && wine hh.exe
+        ;;
+esac
+
+env >> test_env.log
+
+if [ -n "${CC+x}" ]; then
+    # The MSVC compiler "cl" doesn't understand "-v"
+    $CC -v || true
+fi
+if [ "$WITH_VALGRIND" = "yes" ]; then
+    valgrind --version
+fi
+if [ -n "$WRAPPER_CMD" ]; then
+    $WRAPPER_CMD --version
+fi
+
+./autogen.sh
+
+./configure \
+    --enable-experimental="$EXPERIMENTAL" \
+    --with-test-override-wide-multiply="$WIDEMUL" --with-asm="$ASM" \
+    --with-ecmult-window="$ECMULTWINDOW" \
+    --with-ecmult-gen-precision="$ECMULTGENPRECISION" \
+    --enable-module-ecdh="$ECDH" --enable-module-recovery="$RECOVERY" \
+    --enable-module-schnorrsig="$SCHNORRSIG" \
+    --enable-examples="$EXAMPLES" \
+    --enable-ctime-tests="$CTIMETESTS" \
+    --with-valgrind="$WITH_VALGRIND" \
+    --host="$HOST" $EXTRAFLAGS
+
+# We have set "-j<n>" in MAKEFLAGS.
+make
+
+# Print information about binaries so that we can see that the architecture is correct
+file *tests* || true
+file bench* || true
+file .libs/* || true
+
+# This tells `make check` to wrap test invocations.
+export LOG_COMPILER="$WRAPPER_CMD"
+
+make "$BUILD"
+
+# Using the local `libtool` because on macOS the system's libtool has nothing to do with GNU libtool
+EXEC='./libtool --mode=execute'
+if [ -n "$WRAPPER_CMD" ]
+then
+    EXEC="$EXEC $WRAPPER_CMD"
+fi
+
+if [ "$BENCH" = "yes" ]
+then
+    {
+        $EXEC ./bench_ecmult
+        $EXEC ./bench_internal
+        $EXEC ./bench
+    } >> bench.log 2>&1
+fi
+
+if [ "$CTIMETESTS" = "yes" ]
+then
+    if [ "$WITH_VALGRIND" = "yes" ]; then
+        ./libtool --mode=execute valgrind --error-exitcode=42 ./ctime_tests > ctime_tests.log 2>&1
+    else
+        $EXEC ./ctime_tests > ctime_tests.log 2>&1
+    fi
+fi
+
+# Rebuild precomputed files (if not cross-compiling).
+if [ -z "$HOST" ]
+then
+    make clean-precomp
+    make precomp
+fi
+
+# Check that no repo files have been modified by the build.
+# (This fails for example if the precomp files need to be updated in the repo.)
+git diff --exit-code
diff --git a/src/secp256k1/cmake/Check64bitAssembly.cmake b/src/secp256k1/cmake/Check64bitAssembly.cmake
new file mode 100644
index 0000000000..3f65887765
--- /dev/null
+++ b/src/secp256k1/cmake/Check64bitAssembly.cmake
@@ -0,0 +1,14 @@
+include(CheckCSourceCompiles)
+
+function(check_64bit_assembly)
+  check_c_source_compiles("
+    #include <stdint.h>
+
+    int main()
+    {
+      uint64_t a = 11, tmp;
+      __asm__ __volatile__(\"movq $0x100000000,%1; mulq %%rsi\" : \"+a\"(a) : \"S\"(tmp) : \"cc\", \"%rdx\");
+    }
+  " HAS_64BIT_ASM)
+  set(HAS_64BIT_ASM ${HAS_64BIT_ASM} PARENT_SCOPE)
+endfunction()
diff --git a/src/secp256k1/cmake/TryAddCompileOption.cmake b/src/secp256k1/cmake/TryAddCompileOption.cmake
new file mode 100644
index 0000000000..f53c252c2d
--- /dev/null
+++ b/src/secp256k1/cmake/TryAddCompileOption.cmake
@@ -0,0 +1,23 @@
+include(CheckCCompilerFlag)
+
+function(try_add_compile_option option)
+  string(MAKE_C_IDENTIFIER ${option} result)
+  string(TOUPPER ${result} result)
+  set(result "C_SUPPORTS${result}")
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+  if(NOT MSVC)
+    set(CMAKE_REQUIRED_FLAGS "-Werror")
+  endif()
+  check_c_compiler_flag(${option} ${result})
+  if(${result})
+    get_property(compile_options
+      DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+      PROPERTY COMPILE_OPTIONS
+    )
+    list(APPEND compile_options "${option}")
+    set_property(
+      DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+      PROPERTY COMPILE_OPTIONS "${compile_options}"
+    )
+  endif()
+endfunction()