[flang-commits] [clang] [flang] [mlir] [flang] Add support for -mrecip[=<list>] (PR #143418)

[Tarun Prabhu via flang-commits]

================
@@ -3189,3 +3189,144 @@ StringRef tools::ParseMPreferVectorWidthOption(clang::DiagnosticsEngine &Diags,
 
   return Value;
 }
+
+// This is a helper function for validating the optional refinement step
+// parameter in reciprocal argument strings. Return false if there is an error
+// parsing the refinement step. Otherwise, return true and set the Position
+// of the refinement step in the input string.
+static bool getRefinementStep(StringRef In, clang::DiagnosticsEngine &Diags,
+                              const Arg &A, size_t &Position) {
+  const char RefinementStepToken = ':';
+  Position = In.find(RefinementStepToken);
+  if (Position != StringRef::npos) {
+    StringRef Option = A.getOption().getName();
+    StringRef RefStep = In.substr(Position + 1);
+    // Allow exactly one numeric character for the additional refinement
+    // step parameter. This is reasonable for all currently-supported
+    // operations and architectures because we would expect that a larger value
+    // of refinement steps would cause the estimate "optimization" to
+    // under-perform the native operation. Also, if the estimate does not
+    // converge quickly, it probably will not ever converge, so further
+    // refinement steps will not produce a better answer.
+    if (RefStep.size() != 1) {
+      Diags.Report(diag::err_drv_invalid_value) << Option << RefStep;
+      return false;
+    }
+    char RefStepChar = RefStep[0];
+    if (RefStepChar < '0' || RefStepChar > '9') {
+      Diags.Report(diag::err_drv_invalid_value) << Option << RefStep;
+      return false;
+    }
+  }
+  return true;
+}
+
+// Parse -mrecip. Return the Value string if well-formed.
+// Otherwise, return an empty string and issue a diagnosic message if needed.
+StringRef tools::ParseMRecipOption(clang::DiagnosticsEngine &Diags,
----------------
tarunprabhu wrote:

Most functions defined/moved to this file are named with a lowercase starting letter. It might be worth doing the same for this (and I did miss this in `prefer-vector-width` implementation earlier)

```suggestion
StringRef tools::parseMRecipOption(clang::DiagnosticsEngine &Diags,
```

https://github.com/llvm/llvm-project/pull/143418