[flang] Place MIN/MAX A1/A2 first in semantic analysis (#69722)

Intrinsic analysis in semantics reorder the actual arguments so that
they match the dummy order. This was not done for MIN/MAX because they
are special: these are the only intrinsics with a variadic number of
arguments.

This caused bugs in lowering that only check the optionality of actual
arguments from the third position (since A1 and A2 are mandatory).

Update semantics to place A1/A2 first. This also allow removing some
checks that were specific to MIN/MAX. There is no point in
sorting/placing the rest of the arguments which would be tedious and
tricky because of the variadic aspect.

1 files changed, 62 insertions, 72 deletions

diff --git a/flang/lib/Evaluate/intrinsics.cpp b/flang/lib/Evaluate/intrinsics.cpp
index 19cb556..e4125f6 100644
--- a/flang/lib/Evaluate/intrinsics.cpp
+++ b/flang/lib/Evaluate/intrinsics.cpp
@@ -1446,63 +1446,75 @@ static std::int64_t GetBuiltinKind(
 
 // Ensure that the keywords of arguments to MAX/MIN and their variants
 // are of the form A123 with no duplicates or leading zeroes.
-static bool CheckMaxMinArgument(std::optional<parser::CharBlock> keyword,
+static bool CheckMaxMinArgument(parser::CharBlock keyword,
     std::set<parser::CharBlock> &set, const char *intrinsicName,
     parser::ContextualMessages &messages) {
-  if (keyword) {
-    std::size_t j{1};
-    for (; j < keyword->size(); ++j) {
-      char ch{(*keyword)[j]};
-      if (ch < (j == 1 ? '1' : '0') || ch > '9') {
-        break;
-      }
+  std::size_t j{1};
+  for (; j < keyword.size(); ++j) {
+    char ch{(keyword)[j]};
+    if (ch < (j == 1 ? '1' : '0') || ch > '9') {
+      break;
     }
-    if (keyword->size() < 2 || (*keyword)[0] != 'a' || j < keyword->size()) {
-      messages.Say(*keyword,
-          "Argument keyword '%s=' is not known in call to '%s'"_err_en_US,
-          *keyword, intrinsicName);
+  }
+  if (keyword.size() < 2 || (keyword)[0] != 'a' || j < keyword.size()) {
+    messages.Say(keyword,
+        "argument keyword '%s=' is not known in call to '%s'"_err_en_US,
+        keyword, intrinsicName);
+    return false;
+  }
+  if (!set.insert(keyword).second) {
+    messages.Say(keyword,
+        "argument keyword '%s=' was repeated in call to '%s'"_err_en_US,
+        keyword, intrinsicName);
+    return false;
+  }
+  return true;
+}
+
+// Validate the keyword, if any, and ensure that A1 and A2 are always placed in
+// first and second position in actualForDummy. A1 and A2 are special since they
+// are not optional. The rest of the arguments are not sorted, there are no
+// differences between them.
+static bool CheckAndPushMinMaxArgument(ActualArgument &arg,
+    std::vector<ActualArgument *> &actualForDummy,
+    std::set<parser::CharBlock> &set, const char *intrinsicName,
+    parser::ContextualMessages &messages) {
+  if (std::optional<parser::CharBlock> keyword{arg.keyword()}) {
+    if (!CheckMaxMinArgument(*keyword, set, intrinsicName, messages)) {
       return false;
     }
-    auto [_, wasInserted]{set.insert(*keyword)};
-    if (!wasInserted) {
+    const bool isA1{*keyword == parser::CharBlock{"a1", 2}};
+    if (isA1 && !actualForDummy[0]) {
+      actualForDummy[0] = &arg;
+      return true;
+    }
+    const bool isA2{*keyword == parser::CharBlock{"a2", 2}};
+    if (isA2 && !actualForDummy[1]) {
+      actualForDummy[1] = &arg;
+      return true;
+    }
+    if (isA1 || isA2) {
+      // Note that for arguments other than a1 and a2, this error will be caught
+      // later in check-call.cpp.
       messages.Say(*keyword,
-          "Argument keyword '%s=' was repeated in call to '%s'"_err_en_US,
+          "keyword argument '%s=' to intrinsic '%s' was supplied "
+          "positionally by an earlier actual argument"_err_en_US,
           *keyword, intrinsicName);
       return false;
     }
-  }
-  return true;
-}
-
-static void CheckMaxMinA1A2Argument(const ActualArguments &arguments,
-    std::set<parser::CharBlock> &set, parser::ContextualMessages &messages) {
-  parser::CharBlock kwA1{"a1", 2};
-  parser::CharBlock kwA2{"a2", 2};
-  bool missingA1{set.find(kwA1) == set.end()};
-  bool missingA2{set.find(kwA2) == set.end()};
-
-  if (arguments.size() > 1) {
-    if (arguments.at(0)->keyword()) {
-      // If the keyword is specified in the first argument, the following
-      // arguments must have the keywords.
-      if (missingA1 && missingA2) {
-        messages.Say("missing mandatory '%s=' and '%s=' arguments"_err_en_US,
-            kwA1.ToString(), kwA2.ToString());
-      } else if (missingA1 && !missingA2) {
-        messages.Say(
-            "missing mandatory '%s=' argument"_err_en_US, kwA1.ToString());
-      } else if (!missingA1 && missingA2) {
-        messages.Say(
-            "missing mandatory '%s=' argument"_err_en_US, kwA2.ToString());
-      }
-    } else if (arguments.at(1)->keyword()) {
-      // No keyword is specified in the first argument.
-      if (missingA1 && missingA2) {
-        messages.Say(
-            "missing mandatory '%s=' argument"_err_en_US, kwA2.ToString());
+  } else {
+    if (actualForDummy.size() == 2) {
+      if (!actualForDummy[0] && !actualForDummy[1]) {
+        actualForDummy[0] = &arg;
+        return true;
+      } else if (!actualForDummy[1]) {
+        actualForDummy[1] = &arg;
+        return true;
       }
     }
   }
+  actualForDummy.push_back(&arg);
+  return true;
 }
 
 static bool CheckAtomicKind(const ActualArgument &arg,
@@ -1552,7 +1564,7 @@ std::optional<SpecificCall> IntrinsicInterface::Match(
   bool isMaxMin{dummyArgPatterns > 0 &&
       dummy[dummyArgPatterns - 1].optionality == Optionality::repeats};
   std::vector<ActualArgument *> actualForDummy(
-      isMaxMin ? 0 : dummyArgPatterns, nullptr);
+      isMaxMin ? 2 : dummyArgPatterns, nullptr);
   bool anyMissingActualArgument{false};
   std::set<parser::CharBlock> maxMinKeywords;
   bool anyKeyword{false};
@@ -1579,9 +1591,8 @@ std::optional<SpecificCall> IntrinsicInterface::Match(
       continue;
     }
     if (isMaxMin) {
-      if (CheckMaxMinArgument(arg->keyword(), maxMinKeywords, name, messages)) {
-        actualForDummy.push_back(&*arg);
-      } else {
+      if (!CheckAndPushMinMaxArgument(
+              *arg, actualForDummy, maxMinKeywords, name, messages)) {
         return std::nullopt;
       }
     } else {
@@ -1627,17 +1638,6 @@ std::optional<SpecificCall> IntrinsicInterface::Match(
     }
   }
 
-  if (isMaxMin) {
-    int nArgs{0};
-    // max() / max(x) is invalid
-    while ((arguments.size() + nArgs) < 2) {
-      actualForDummy.push_back(nullptr);
-      nArgs++;
-    }
-
-    CheckMaxMinA1A2Argument(arguments, maxMinKeywords, messages);
-  }
-
   std::size_t dummies{actualForDummy.size()};
 
   // Check types and kinds of the actual arguments against the intrinsic's
@@ -1659,18 +1659,8 @@ std::optional<SpecificCall> IntrinsicInterface::Match(
     if (!arg) {
       if (d.optionality == Optionality::required) {
         std::string kw{d.keyword};
-        if (isMaxMin && maxMinKeywords.size() == 1) {
-          // max(a1=x) or max(a2=x)
-          const auto kwA1{dummy[0].keyword};
-          const auto kwA2{dummy[1].keyword};
-          if (maxMinKeywords.begin()->ToString() == kwA1) {
-            messages.Say("missing mandatory 'a2=' argument"_err_en_US);
-          } else if (maxMinKeywords.begin()->ToString() == kwA2) {
-            messages.Say("missing mandatory 'a1=' argument"_err_en_US);
-          } else {
-            messages.Say(
-                "missing mandatory 'a1=' and 'a2=' arguments"_err_en_US);
-          }
+        if (isMaxMin && !actualForDummy[0] && !actualForDummy[1]) {
+          messages.Say("missing mandatory 'a1=' and 'a2=' arguments"_err_en_US);
         } else {
           messages.Say(
               "missing mandatory '%s=' argument"_err_en_US, kw.c_str());