[flang] Place MIN/MAX A1/A2 first in semantic analysis

[jeanPerier]

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.

[llvmbot]

@llvm/pr-subscribers-flang-fir-hlfir

@llvm/pr-subscribers-flang-semantics

Author: None (jeanPerier)

Changes

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.

---

Full diff: https://github.com/llvm/llvm-project/pull/69722.diff

4 Files Affected:

• (modified) flang/include/flang/Evaluate/intrinsics.h (+3)
• (modified) flang/lib/Evaluate/intrinsics.cpp (+63-72)
• (added) flang/test/Lower/Intrinsics/min.f90 (+34)
• (modified) flang/test/Semantics/call23.f90 (+15-7)

diff --git a/flang/include/flang/Evaluate/intrinsics.h b/flang/include/flang/Evaluate/intrinsics.h
index 5e06fcba389b278..15afb772ae767b8 100644
--- a/flang/include/flang/Evaluate/intrinsics.h
+++ b/flang/include/flang/Evaluate/intrinsics.h
@@ -99,6 +99,9 @@ class IntrinsicProcTable {
   // On success, the actual arguments are transferred to the result
   // in dummy argument order; on failure, the actual arguments remain
   // untouched.
+  // For MIN and MAX, only a1 and a2 actual arguments are transferred in dummy
+  // order on success and the other arguments are transferred afterwards
+  // without being sorted.
   std::optional<SpecificCall> Probe(
       const CallCharacteristics &, ActualArguments &, FoldingContext &) const;
 
diff --git a/flang/lib/Evaluate/intrinsics.cpp b/flang/lib/Evaluate/intrinsics.cpp
index 19cb556c2380c62..cf1008af116ab62 100644
--- a/flang/lib/Evaluate/intrinsics.cpp
+++ b/flang/lib/Evaluate/intrinsics.cpp
@@ -1446,63 +1446,76 @@ 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;
+  }
+  auto [_, wasInserted]{set.insert(keyword)};
+  if (!wasInserted) {
+    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 +1565,7 @@ 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 +1592,8 @@ 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 +1639,6 @@ 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 +1660,8 @@ 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());
diff --git a/flang/test/Lower/Intrinsics/min.f90 b/flang/test/Lower/Intrinsics/min.f90
new file mode 100644
index 000000000000000..40e6d96db6e53e7
--- /dev/null
+++ b/flang/test/Lower/Intrinsics/min.f90
@@ -0,0 +1,34 @@
+! RUN: bbc -emit-hlfir -o - %s 2>&1 | FileCheck %s
+! Test that min/max A(X>2) optional arguments are handled regardless
+! of the order in which they appear. Only A1 and A2 are mandatory.
+
+real function test(a, b, c)
+  real, optional :: a, b, c
+  test = min(a1=a, a3=c, a2=c)
+end function
+! CHECK-LABEL:   func.func @_QPtest(
+! CHECK-SAME:                       %[[VAL_0:.*]]: !fir.ref<f32> {fir.bindc_name = "a", fir.optional},
+! CHECK-SAME:                       %[[VAL_1:.*]]: !fir.ref<f32> {fir.bindc_name = "b", fir.optional},
+! CHECK-SAME:                       %[[VAL_2:.*]]: !fir.ref<f32> {fir.bindc_name = "c", fir.optional}) -> f32 {
+! CHECK:           %[[VAL_3:.*]]:2 = hlfir.declare %[[VAL_0]] {{.*}}uniq_name = "_QFtestEa"}
+! CHECK:           %[[VAL_4:.*]]:2 = hlfir.declare %[[VAL_1]] {{.*}}uniq_name = "_QFtestEb"}
+! CHECK:           %[[VAL_5:.*]]:2 = hlfir.declare %[[VAL_2]] {{.*}}uniq_name = "_QFtestEc"}
+! CHECK:           %[[VAL_6:.*]] = fir.alloca f32 {bindc_name = "test", uniq_name = "_QFtestEtest"}
+! CHECK:           %[[VAL_7:.*]]:2 = hlfir.declare %[[VAL_6]] {uniq_name = "_QFtestEtest"} : (!fir.ref<f32>) -> (!fir.ref<f32>, !fir.ref<f32>)
+! CHECK:           %[[VAL_8:.*]] = fir.load %[[VAL_3]]#0 : !fir.ref<f32>
+! CHECK:           %[[VAL_9:.*]] = fir.load %[[VAL_5]]#0 : !fir.ref<f32>
+! CHECK:           %[[VAL_10:.*]] = fir.is_present %[[VAL_5]]#0 : (!fir.ref<f32>) -> i1
+! CHECK:           %[[VAL_11:.*]] = arith.cmpf olt, %[[VAL_8]], %[[VAL_9]] : f32
+! CHECK:           %[[VAL_12:.*]] = arith.select %[[VAL_11]], %[[VAL_8]], %[[VAL_9]] : f32
+! CHECK:           %[[VAL_13:.*]] = fir.if %[[VAL_10]] -> (f32) {
+! CHECK:             %[[VAL_14:.*]] = fir.load %[[VAL_5]]#0 : !fir.ref<f32>
+! CHECK:             %[[VAL_15:.*]] = arith.cmpf olt, %[[VAL_12]], %[[VAL_14]] : f32
+! CHECK:             %[[VAL_16:.*]] = arith.select %[[VAL_15]], %[[VAL_12]], %[[VAL_14]] : f32
+! CHECK:             fir.result %[[VAL_16]] : f32
+! CHECK:           } else {
+! CHECK:             fir.result %[[VAL_12]] : f32
+! CHECK:           }
+! CHECK:           hlfir.assign %[[VAL_13]] to %[[VAL_7]]#0 : f32, !fir.ref<f32>
+! CHECK:           %[[VAL_17:.*]] = fir.load %[[VAL_7]]#1 : !fir.ref<f32>
+! CHECK:           return %[[VAL_17]] : f32
+! CHECK:         }
diff --git a/flang/test/Semantics/call23.f90 b/flang/test/Semantics/call23.f90
index 38c860ad3b51670..e5c205dba885e5f 100644
--- a/flang/test/Semantics/call23.f90
+++ b/flang/test/Semantics/call23.f90
@@ -1,15 +1,15 @@
 ! RUN: %python %S/test_errors.py %s %flang_fc1
 ! Check errors on MAX/MIN with keywords, a weird case in Fortran
 real :: x = 0.0, y = 0.0 , y1 = 0.0 ! prevent folding
-!ERROR: Argument keyword 'a1=' was repeated in call to 'max'
+!ERROR: argument keyword 'a1=' was repeated in call to 'max'
 print *, max(a1=x,a1=1)
-!ERROR: Keyword argument 'a1=' has already been specified positionally (#1) in this procedure reference
+!ERROR: keyword argument 'a1=' to intrinsic 'max' was supplied positionally by an earlier actual argument
 print *, max(x,a1=1)
-!ERROR: Keyword argument 'a1=' has already been specified positionally (#1) in this procedure reference
+!ERROR: keyword argument 'a1=' to intrinsic 'min1' was supplied positionally by an earlier actual argument
 print *, min1(1.,a1=2.,a2=3.)
 print *, max(a1=x,a2=0,a4=0) ! ok
 print *, max(x,0,a99=0) ! ok
-!ERROR: Argument keyword 'a06=' is not known in call to 'max'
+!ERROR: argument keyword 'a06=' is not known in call to 'max'
 print *, max(a1=x,a2=0,a06=0)
 !ERROR: missing mandatory 'a2=' argument
 print *, max(a3=y, a1=x)
@@ -29,10 +29,18 @@
 print *, max(a2=y)
 !ERROR: missing mandatory 'a1=' and 'a2=' arguments
 print *, max(a3=x)
-!ERROR: Argument keyword 'a0=' is not known in call to 'max'
+!ERROR: argument keyword 'a0=' is not known in call to 'max'
 print *, max(a0=x)
-!ERROR: Argument keyword 'a03=' is not known in call to 'max'
+!ERROR: argument keyword 'a03=' is not known in call to 'max'
 print *, max(a03=x)
-!ERROR: Argument keyword 'abad=' is not known in call to 'max'
+!ERROR: argument keyword 'abad=' is not known in call to 'max'
 print *, max(abad=x)
+!ERROR: actual argument #2 without a keyword may not follow an actual argument with a keyword
+print *, max(a1=x, y)
+!ERROR: Keyword argument 'a3=' has already been specified positionally (#3) in this procedure reference
+print *, max(x, y, y1, a3=x)
+print *, max(a3=x, a4=x, a2=x, a1=x) ! ok
+print *, max(a3=x, a2=y, a4=x, a1=x) ! ok
+print *, max(x, a2=y, a5=x, a4=x) ! ok
+print *, max(x, y, a4=x, a6=x) ! ok
 end