Update comments

Author: taiki-e

build.rs

@@ -249,7 +249,7 @@ fn main() {
                 // (Since Rust 1.78, Windows (except Windows 7) targets also enable CMPXCHG16B, but
                 // this branch is only used on pre-1.69 that cmpxchg16b_target_feature is unstable.)
                 // Script to get builtin targets that support CMPXCHG16B by default:
-                // $ (for target in $(rustc --print target-list | grep -E '^x86_64'); do rustc --print cfg --target "${target}" | grep -Fq '"cmpxchg16b"' && printf '%s\n' "${target}"; done)
+                // $ (for target in $(rustc -Z unstable-options --print all-target-specs-json | jq -r '. | to_entries[] | if .value.arch == "x86_64" then .key else empty end'); do rustc --print cfg --target "${target}" | grep -Fq '"cmpxchg16b"' && printf '%s\n' "${target}"; done)
                 let is_apple = env::var("CARGO_CFG_TARGET_VENDOR").unwrap_or_default() == "apple";
                 let cmpxchg16b = is_apple;
                 // LLVM recognizes this also as cx16 target feature: https://godbolt.org/z/KM3jz616j
@@ -271,8 +271,8 @@ fn main() {
                 // https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/AArch64/AArch64Processors.td#L1203
                 // https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/AArch64/AArch64Processors.td#L865
                 // Script to get builtin targets that support FEAT_LSE/FEAT_LSE2 by default:
-                // $ (for target in $(rustc --print target-list | grep -E '^aarch64|^arm64'); do rustc --print cfg --target "${target}" | grep -Fq '"lse"' && printf '%s\n' "${target}"; done)
-                // $ (for target in $(rustc --print target-list | grep -E '^aarch64|^arm64'); do rustc --print cfg --target "${target}" | grep -Fq '"lse2"' && printf '%s\n' "${target}"; done)
+                // $ (for target in $(rustc -Z unstable-options --print all-target-specs-json | jq -r '. | to_entries[] | if .value.arch == "aarch64" or .value.arch == "arm64ec" then .key else empty end'); do rustc --print cfg --target "${target}" | grep -Fq '"lse"' && printf '%s\n' "${target}"; done)
+                // $ (for target in $(rustc -Z unstable-options --print all-target-specs-json | jq -r '. | to_entries[] | if .value.arch == "aarch64" or .value.arch == "arm64ec" then .key else empty end'); do rustc --print cfg --target "${target}" | grep -Fq '"lse2"' && printf '%s\n' "${target}"; done)
                 let is_macos = target_os == "macos";
                 let mut lse = is_macos;
                 target_feature_fallback("lse2", is_macos);

tools/no-std.sh

@@ -9,6 +9,7 @@ cd -- "$(dirname -- "$0")"/..
 # USAGE:
 #    ./tools/no-std.sh [+toolchain] [target]...
 
+# rustc -Z unstable-options --print all-target-specs-json | jq -r '. | to_entries[] | if .value.os then empty else .key end'
 default_targets=(
   # arm
   # v4T