[lld] [AArch64][GCS][LLD] Introduce -zgcs-report-dynamic Command Line Option (PR #127787)

[Fangrui Song via llvm-commits]

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@@ -569,6 +576,58 @@ static GcsPolicy getZGcs(Ctx &ctx, opt::InputArgList &args) {
   return ret;
 }
 
+static GcsReportPolicy getZGcsReport(Ctx &ctx, opt::InputArgList &args) {
+  GcsReportPolicy ret = GcsReportPolicy::None;
+
+  for (auto *arg : args.filtered(OPT_z)) {
+    std::pair<StringRef, StringRef> kv = StringRef(arg->getValue()).split('=');
+    if (kv.first == "gcs-report") {
+      arg->claim();
+      if (kv.second == "none")
+        ret = GcsReportPolicy::None;
+      else if (kv.second == "warning")
+        ret = GcsReportPolicy::Warning;
+      else if (kv.second == "error")
+        ret = GcsReportPolicy::Error;
+      else
+        ErrAlways(ctx) << "unknown -z gcs-report= value: " << kv.second;
+    }
+  }
+
+  return ret;
+}
+
+static GcsReportPolicy getZGcsReportDynamic(Ctx &ctx, opt::InputArgList &args) {
+  GcsReportPolicy ret = GcsReportPolicy::None;
+  for (auto *arg : args.filtered(OPT_z)) {
+    std::pair<StringRef, StringRef> kv = StringRef(arg->getValue()).split('=');
+    if (kv.first == "gcs-report-dynamic") {
+      arg->claim();
+      if (kv.second == "none")
+        ret = GcsReportPolicy::None;
+      else if (kv.second == "warning")
+        ret = GcsReportPolicy::Warning;
+      else if (kv.second == "error")
+        ret = GcsReportPolicy::Error;
+      else
+        ErrAlways(ctx) << "unknown -z gcs-report-dynamic= value: " << kv.second;
+      // once the gcs-report-dynamic option has been processed, we want to break
+      // from the loop to ensure we do not overwrite the return value if the
+      // user has also passed a value for the gcs-report option.
+      break;
+    }
+    // If the user has not defined a value for gcs-report-dynamic, but has for
+    // gcs-report, we want to inherit that value for gcs-report-dynamic. This is
+    // capped at a warning to ensure a users module can still build, while
+    // providing information relating to if a dynamic object supports GCS.
+    if (kv.first == "gcs-report" &&
----------------
MaskRay wrote:

Probably 

* Combine getZGcsReport and getZGcsReportDynamic
* Keep the last values of gcs-report and gcs-report-dynamic, respectively, in different variables.

Then one loop suffices. 

https://github.com/llvm/llvm-project/pull/127787