[flang] Add parsing-support for IVDEP directive

flang/docs/Directives.md

@@ -39,6 +39,8 @@ A list of non-standard directives supported by Flang
 * `!dir$ vector always` forces vectorization on the following loop regardless
   of cost model decisions. The loop must still be vectorizable.
   [This directive currently only works on plain do loops without labels].
+* `!dir$ ivdep` tells vectorization to ignore the dependency analysis of the
+  following loop.
 
 # Directive Details
 

flang/include/flang/Parser/dump-parse-tree.h

@@ -203,6 +203,7 @@ class ParseTreeDumper {
   NODE(parser, CompilerDirective)
   NODE(CompilerDirective, AssumeAligned)
   NODE(CompilerDirective, IgnoreTKR)
+  NODE(CompilerDirective, IgnoreVectorDep)
   NODE(CompilerDirective, LoopCount)
   NODE(CompilerDirective, NameValue)
   NODE(CompilerDirective, Unrecognized)

flang/include/flang/Parser/parse-tree.h

@@ -3342,10 +3342,12 @@ struct CompilerDirective {
     TUPLE_CLASS_BOILERPLATE(NameValue);
     std::tuple<Name, std::optional<std::uint64_t>> t;
   };
+  EMPTY_CLASS(IgnoreVectorDep);
   EMPTY_CLASS(Unrecognized);
   CharBlock source;
-  std::variant<std::list<IgnoreTKR>, LoopCount, std::list<AssumeAligned>,
-      VectorAlways, std::list<NameValue>, Unrecognized>
+  std::variant<std::list<IgnoreTKR>, IgnoreVectorDep, LoopCount,
+      std::list<AssumeAligned>, VectorAlways, std::list<NameValue>,
+      Unrecognized>
       u;
 };
 

flang/lib/Parser/Fortran-parsers.cpp

@@ -1266,12 +1266,15 @@ TYPE_PARSER(construct<StatOrErrmsg>("STAT =" >> statVariable) ||
 // Directives, extensions, and deprecated statements
 // !DIR$ IGNORE_TKR [ [(tkrdmac...)] name ]...
 // !DIR$ LOOP COUNT (n1[, n2]...)
+// !DIR$ IVDEP
 // !DIR$ name[=value] [, name[=value]]...
 // !DIR$ <anything else>
 constexpr auto ignore_tkr{
     "IGNORE_TKR" >> optionalList(construct<CompilerDirective::IgnoreTKR>(
                         maybe(parenthesized(many(letter))), name))};
-constexpr auto loopCount{
+constexpr auto ignoreVectorDep{
+    "IVDEP" >> construct<CompilerDirective::IgnoreVectorDep>()};
+const constexpr auto loopCount{
     "LOOP COUNT" >> construct<CompilerDirective::LoopCount>(
                         parenthesized(nonemptyList(digitString64)))};
 constexpr auto assumeAligned{"ASSUME_ALIGNED" >>
@@ -1283,6 +1286,7 @@ TYPE_PARSER(beginDirective >> "DIR$ "_tok >>
     sourced((construct<CompilerDirective>(ignore_tkr) ||
                 construct<CompilerDirective>(loopCount) ||
                 construct<CompilerDirective>(assumeAligned) ||
+                construct<CompilerDirective>(ignoreVectorDep) ||
                 construct<CompilerDirective>(vectorAlways) ||
                 construct<CompilerDirective>(
                     many(construct<CompilerDirective::NameValue>(

flang/lib/Parser/unparse.cpp

@@ -1826,6 +1826,9 @@ class UnparseVisitor {
               Word("!DIR$ IGNORE_TKR"); // emitted even if tkr list is empty
               Walk(" ", tkr, ", ");
             },
+            [&](const CompilerDirective::IgnoreVectorDep &) {
+              Word("!DIR$ IVDEP");
+            },
             [&](const CompilerDirective::LoopCount &lcount) {
               Walk("!DIR$ LOOP COUNT (", lcount.v, ", ", ")");
             },

flang/test/Parser/compiler-directives.f90

@@ -35,3 +35,10 @@ subroutine vector_always
   do i=1,10
   enddo
 end subroutine
+
+subroutine ignore_vector_dep
+  !dir$ ivdep
+  ! CHECK: !DIR$ IVDEP
+  do i=1,10
+  enddo
+end subroutine