processor: fix multi-target matching + validate CPU targets at startup

- sysimg_init_cb: resolve only the first target from the cpu_target
  string (matching old behavior). "native" detects the host; explicit
  names like "haswell" use those features for matching.
- jl_cpu_has_fma: check JIT target features, not host features
- Add jl_check_cpu_target() called from init.c to validate the CPU
  target before sysimage loading: errors on unknown CPU names,
  multiple targets without --output-o, and clone_all without --output-o
- Restore --cpu-target=help support via tp::print_cpu_targets()

Update cpufeatures pin to c64dc9b which excludes ermsb/fsrm from
hw_feature_mask and adds print_cpu_targets().

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: gbaraldi

deps/cpufeatures.version

@@ -3,5 +3,5 @@
 ## source build
 CPUFEATURES_VER := 0.2.0
 CPUFEATURES_GIT_URL := https://github.com/gbaraldi/cpufeatures.git
-CPUFEATURES_TAR_URL := https://github.com/gbaraldi/cpufeatures/archive/09a9c883543ce23c06092a9a473ed76f873bd905.tar.gz
-CPUFEATURES_SHA := 09a9c883543ce23c06092a9a473ed76f873bd905
+CPUFEATURES_TAR_URL := https://github.com/gbaraldi/cpufeatures/archive/0fe7177edcd99a83c6e33b5ce4672079cfbac75c.tar.gz
+CPUFEATURES_SHA := 0fe7177edcd99a83c6e33b5ce4672079cfbac75c

src/init.c

@@ -585,14 +585,8 @@ static NOINLINE void _finish_jl_init_(jl_image_buf_t sysimage, jl_ptls_t ptls, j
     if (jl_options.cpu_target[0] == '\0')
         jl_error("Invalid target option: empty CPU name");
 
-    // When not generating output, multiple targets and clone_all are not allowed
-    if (!jl_generating_output()) {
-        if (strchr(jl_options.cpu_target, ';') != NULL) {
-            jl_safe_printf("More than one command line CPU targets specified "
-                      "without a `--output-` flag specified");
-            exit(1);
-        }
-    }
+    // Validate CPU target: check for unknown names, multiple targets, clone_all
+    jl_check_cpu_target(jl_options.cpu_target, jl_generating_output());
 
     // Parse image, perform relocations, and init JIT targets, etc.
     jl_image_t parsed_image = jl_init_processor_sysimg(sysimage, jl_options.cpu_target);

src/processor.cpp

@@ -374,19 +374,6 @@ static void ensure_jit_target(const char *cpu_target, bool imaging)
     if (specs.empty())
         jl_error("No targets specified");
 
-    if (!imaging) {
-        if (specs.size() > 1) {
-            jl_safe_printf("More than one command line CPU targets specified "
-                      "without a `--output-` flag specified");
-            exit(1);
-        }
-        if (specs[0].flags & tp::TF_CLONE_ALL) {
-            jl_safe_printf("\"clone_all\" feature specified "
-                      "without a `--output-` flag specified");
-            exit(1);
-        }
-    }
-
     // Set clone flags from feature diffs
     for (size_t i = 1; i < specs.size(); i++) {
         if (specs[i].flags & tp::TF_CLONE_ALL) {
@@ -414,9 +401,20 @@ static uint32_t sysimg_init_cb(void *ctx, const void *id, jl_value_t **rejection
     CF_DEBUG("[cpufeatures] sysimg_init_cb: cpu_target='%s'\n",
              cpu_target ? cpu_target : "(null)");
 
-    // Resolve JIT target against host
+    // Resolve the first target from the cpu_target string.
+    // "native" expands to the detected host CPU. For multi-target strings
+    // (sysimage building), only the first target is used for matching.
     auto target_str = expand_cpu_target(cpu_target);
-    auto host_specs = tp::resolve_targets_for_llvm(target_str);
+    std::string first_target;
+    auto semi = target_str.find(';');
+    if (semi != std::string::npos)
+        first_target = target_str.substr(0, semi);
+    else
+        first_target = target_str;
+    if (first_target.empty())
+        first_target = "native";
+
+    auto host_specs = tp::resolve_targets_for_llvm(first_target);
     if (host_specs.empty())
         jl_error("No targets specified");
 
@@ -611,6 +609,47 @@ JL_DLLEXPORT jl_value_t *jl_cpu_has_fma(int bits)
     return jl_false;
 }
 
+// Validate cpu_target string before any processing.
+// Called from init.c early in startup.
+extern "C" JL_DLLEXPORT void jl_check_cpu_target(const char *cpu_target, int imaging)
+{
+    init_feature_names();
+    if (!cpu_target || !*cpu_target)
+        return; // NULL/empty handled elsewhere
+
+    auto target_str = expand_cpu_target(cpu_target);
+    if (target_str.empty())
+        return;
+
+    // Handle "help": print available CPU targets and exit
+    if (target_str == "help" || target_str.find(",help") != std::string::npos) {
+        tp::print_cpu_targets();
+        exit(0);
+    }
+
+    auto specs = tp::resolve_targets_for_llvm(target_str);
+
+    for (auto &s : specs) {
+        if (s.flags & tp::TF_UNKNOWN_NAME) {
+            jl_safe_printf("Unknown cpu target: \"%s\"\n", s.cpu_name.c_str());
+            exit(1);
+        }
+    }
+
+    if (!imaging) {
+        if (specs.size() > 1) {
+            jl_safe_printf("More than one command line CPU targets specified "
+                      "without a `--output-` flag specified");
+            exit(1);
+        }
+        if (!specs.empty() && (specs[0].flags & tp::TF_CLONE_ALL)) {
+            jl_safe_printf("\"clone_all\" feature specified "
+                      "without a `--output-` flag specified");
+            exit(1);
+        }
+    }
+}
+
 jl_image_t jl_init_processor_sysimg(jl_image_buf_t image, const char *cpu_target)
 {
     init_feature_names();

src/processor.h

@@ -199,6 +199,7 @@ typedef struct {
  *
  * Return the data about the function pointers selected.
  */
+void jl_check_cpu_target(const char *cpu_target, int imaging);
 jl_image_t jl_init_processor_sysimg(jl_image_buf_t image, const char *cpu_target);
 jl_image_t jl_init_processor_pkgimg(jl_image_buf_t image);
 

test/cmdlineargs.jl

@@ -197,6 +197,13 @@ end
     wait(p)
     @test p.exitcode == 1
     @test occursin("empty CPU name", String(take!(io)))
+
+    # Test --cpu-target=help prints available targets and exits cleanly
+    let v = readchomperrors(`$(Base.julia_cmd(; cpu_target="help"))`)
+        @test v[1] == true  # exits with 0
+        @test occursin("Available CPU targets:", v[2])
+        @test occursin("Host CPU:", v[2])
+    end
 end
 
 let exename = `$(Base.julia_cmd()) --startup-file=no --color=no`