Swap default-cpu for sandybridge and use it when compiling libsecp

sandybridge is a reasonable choice because it supports AVX but is
also 10+ years old (with AMD support for AVX at similar times).

The next option would be haswell with AVX2, which doesn't add as
much and for which AMD processors only came about in mid-2015.

diff --git a/genbindings.sh b/genbindings.sh
index 406dded6a6ff7c87960be9687ab0ea93ee6164c8..5b1713506c4b87e520784717345808b4bdf1177c 100755 (executable)
--- a/genbindings.sh
+++ b/genbindings.sh
@@ -137,13 +137,15 @@ PATH="$(pwd)/deterministic-build-wrappers:$PATH:~/.cargo/bin"
 cd lightning-c-bindings
 
 # Remap paths so that our builds are deterministic
-export RUSTFLAGS="--remap-path-prefix $LIGHTNING_PATH=rust-lightning --remap-path-prefix $(pwd)=ldk-c-bindings --remap-path-prefix $HOME/.cargo= -C target-cpu=generic"
+export RUSTFLAGS="--remap-path-prefix $LIGHTNING_PATH=rust-lightning --remap-path-prefix $(pwd)=ldk-c-bindings --remap-path-prefix $HOME/.cargo= -C target-cpu=sandybridge"
 
 # If the C compiler supports it, also set -ffile-prefix-map
 echo "int main() {}" > genbindings_path_map_test_file.c
 clang -o /dev/null -ffile-prefix-map=$HOME/.cargo= genbindings_path_map_test_file.c > /dev/null 2>&1 &&
 # Now that we've done our last non-LTO build, turn on LTO in CFLAGS as well
-export CFLAGS="-ffile-prefix-map=$HOME/.cargo="
+export BASE_CFLAGS="-ffile-prefix-map=$HOME/.cargo="
+ENV_TARGET=$(rustc --version --verbose | grep host | awk '{ print $2 }' | sed 's/-/_/g')
+export CFLAGS_$ENV_TARGET="$BASE_CFLAGS -march=sandybridge -mcpu=sandybridge -mtune=sandybridge"
 rm genbindings_path_map_test_file.c
 
 cargo build
@@ -307,7 +309,7 @@ if [ "$HOST_PLATFORM" != "host: x86_64-apple-darwin" -a "$CLANGPP" != "" ]; then
        # The cc-rs crate tries to force -fdata-sections and -ffunction-sections on, which
        # breaks -fembed-bitcode, so we turn off cc-rs' default flags and specify exactly
        # what we want here.
-       export CFLAGS="$CFLAGS -fPIC -fembed-bitcode"
+       export CFLAGS_$ENV_TARGET="$BASE_CFLAGS -fPIC -fembed-bitcode -march=sandybridge"
        export CRATE_CC_NO_DEFAULTS=true
 fi
 
@@ -316,9 +318,9 @@ if [ "$2" = "false" -a "$(rustc --print target-list | grep wasm32-wasi)" != "" ]
        echo "int main() {}" > genbindings_wasm_test_file.c
        if clang -nostdlib -o /dev/null --target=wasm32-wasi -Wl,--no-entry genbindings_wasm_test_file.c > /dev/null 2>&1; then
                # And if it does, build a WASM binary without capturing errors
-               export CFLAGS_wasm32_wasi="-target wasm32"
+               export CFLAGS_wasm32_wasi="$BASE_CFLAGS -target wasm32"
                cargo rustc -v --target=wasm32-wasi
-               export CFLAGS_wasm32_wasi="-target wasm32 -Os"
+               export CFLAGS_wasm32_wasi="$BASE_CFLAGS -target wasm32 -Os"
                CARGO_PROFILE_RELEASE_LTO=true cargo rustc -v --release --target=wasm32-wasi -- -C embed-bitcode=yes -C opt-level=s -C linker-plugin-lto -C lto
        else
                echo "Cannot build WASM lib as clang does not seem to support the wasm32-wasi target"
@@ -332,7 +334,7 @@ if [ "$HOST_PLATFORM" != "host: x86_64-apple-darwin" -a "$CLANGPP" != "" ]; then
        # or Ubuntu packages). This should work fine on Distros which do more involved
        # packaging than simply shipping the rustup binaries (eg Debian should Just Work
        # here).
-       export CFLAGS="$CFLAGS -O3"
+       export CFLAGS_$ENV_TARGET="$BASE_CFLAGS -O3 -fPIC -fembed-bitcode -march=sandybridge"
        # Rust doesn't recognize CFLAGS changes, so we need to clean build artifacts
        cargo clean --release
        CARGO_PROFILE_RELEASE_LTO=true cargo rustc -v --release -- -C linker-plugin-lto -C lto -C link-arg=-fuse-ld=lld