[flang] Add parsing-support for IVDEP directive #101045

Leporacanthicus · 2024-07-29T17:44:20Z

This adds the parser-side of the IVDEP (Ignore Vector memory DEPendencies) directive. This still produces a warning when used at this point.

There will be a follow-up patch to implement the lowering for this, so that it passes attributes to LLVM to indicate that it should ignore memory dependencies for the vectorisation of the loop following the IVDEP directive.

llvmbot · 2024-07-29T17:44:54Z

@llvm/pr-subscribers-flang-parser

Author: Mats Petersson (Leporacanthicus)

Changes

This adds the parser-side of the IVDEP (Ignore Vector memory DEPendencies). This still produces a warning when used at this point.

There will be a follow-up patch to implement the lowering for this, so that it passes attributes to LLVM to indicate that it should ignore memory dependencies for the vectorisation of the loop following the IVDEP directive.

Full diff: https://github.com/llvm/llvm-project/pull/101045.diff

6 Files Affected:

(modified) flang/docs/Directives.md (+2)
(modified) flang/include/flang/Parser/dump-parse-tree.h (+1)
(modified) flang/include/flang/Parser/parse-tree.h (+4-2)
(modified) flang/lib/Parser/Fortran-parsers.cpp (+5-1)
(modified) flang/lib/Parser/unparse.cpp (+3)
(modified) flang/test/Parser/compiler-directives.f90 (+7)

diff --git a/flang/docs/Directives.md b/flang/docs/Directives.md
index f356f762b13a2..2d70a1c4b33be 100644
--- a/flang/docs/Directives.md
+++ b/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$ ivdev` tells vecorisation to ignore the dependency analysis of the
+  following loop.
 
 # Directive Details
 
diff --git a/flang/include/flang/Parser/dump-parse-tree.h b/flang/include/flang/Parser/dump-parse-tree.h
index 37c3370b48a08..2e026e6427a6b 100644
--- a/flang/include/flang/Parser/dump-parse-tree.h
+++ b/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)
diff --git a/flang/include/flang/Parser/parse-tree.h b/flang/include/flang/Parser/parse-tree.h
index 548fcc81984b2..660cd49224301 100644
--- a/flang/include/flang/Parser/parse-tree.h
+++ b/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;
 };
 
diff --git a/flang/lib/Parser/Fortran-parsers.cpp b/flang/lib/Parser/Fortran-parsers.cpp
index 0bdc4c4e033c7..7ae4ae474ac2e 100644
--- a/flang/lib/Parser/Fortran-parsers.cpp
+++ b/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 ignore_vector_dep{
+    "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>(ignore_vector_dep) ||
                 construct<CompilerDirective>(vectorAlways) ||
                 construct<CompilerDirective>(
                     many(construct<CompilerDirective::NameValue>(
diff --git a/flang/lib/Parser/unparse.cpp b/flang/lib/Parser/unparse.cpp
index 2511a5dda9d09..5b4b5adcd4953 100644
--- a/flang/lib/Parser/unparse.cpp
+++ b/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 &ivdep) {
+              Word("!DIR$ IVDEP");
+            },
             [&](const CompilerDirective::LoopCount &lcount) {
               Walk("!DIR$ LOOP COUNT (", lcount.v, ", ", ")");
             },
diff --git a/flang/test/Parser/compiler-directives.f90 b/flang/test/Parser/compiler-directives.f90
index 246eaf985251c..3eac51b6df6d2 100644
--- a/flang/test/Parser/compiler-directives.f90
+++ b/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

klausler · 2024-07-29T18:47:44Z

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$ ivdev` tells vecorisation to ignore the dependency analysis of the


ivdep

vectori[zs]ation

Darn it, missed the first one, fixed the spelling of optimization. Update coming in a few minutes.

klausler · 2024-07-29T18:48:31Z

flang/lib/Parser/Fortran-parsers.cpp

 // !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 ignore_vector_dep{


ignoreVectorDep

I will fix the ignore_tkr -> ignoreTkr (or ingoreTKR) in a follow up commit.

klausler · 2024-07-29T18:49:05Z

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 &ivdep) {


no argument name needed or desired (can raise build warnings)

kiranchandramohan

LG. Please wait for @klausler

There will be a follow-up patch to implement the lowering for this

Did vector always have a semantics portion to warn if it is not applied to loops?

Leporacanthicus · 2024-08-01T14:57:56Z

LG. Please wait for @klausler

There will be a follow-up patch to implement the lowering for this

Did vector always have a semantics portion to warn if it is not applied to loops?

The follow-up patch here is just my intention to unify style and patterns, as there are other cases of the things that was pointed out in this review, that should be "the same".

There will be similar semantics checks (literally just adding another case for this directive), but that's in the "implementation part" that I'm working on right now.

DavidTruby

LGTM but wait for @klausler to approve

klausler · 2024-08-05T15:15:54Z

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 vecorization to ignore the dependency analysis of the


Still missing a 'T'.

Fixed... Sorry about the delay, I was hoping to have the rest of this work ready by today, but it's not there yet, and some other work is currently more important... :(

This adds the parser-side of the IVDEP (Ignore Vector memory DEPendencies). This still produces a warning when used at this point. There will be a follow-up patch to implement the lowering for this, so that it passes attributes to LLVM to indicate that it should ignore memory dependencies for the vectorisation of the loop following the IVDEP directive.

JDPailleux · 2025-04-07T07:07:49Z

@Leporacanthicus Hello, I am currently proposing an implementation for the IVDEP directive. I wanted to know the status of this PR and when it can be merged?

Leporacanthicus requested review from DavidTruby and klausler July 29, 2024 17:44

llvmbot added flang Flang issues not falling into any other category flang:parser labels Jul 29, 2024

klausler reviewed Jul 29, 2024

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kiranchandramohan approved these changes Aug 1, 2024

View reviewed changes

DavidTruby approved these changes Aug 5, 2024

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klausler reviewed Aug 5, 2024

View reviewed changes

Leporacanthicus added 4 commits August 12, 2024 15:37

Fix review comments

896fbdf

Fix minor typo missed previously

6dfa1d1

Fix simple typo

89009da

Leporacanthicus force-pushed the ivdep branch from 64aa0ae to 89009da Compare August 12, 2024 16:49

kiranchandramohan mentioned this pull request Mar 31, 2025

[flang] Implement !DIR$ IVDEP directive #133728

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