[flang-commits] [flang] [flang][OpenMP] Allow 0 after directive sentinels (PR #217124)

[Leandro Lupori via flang-commits]

https://github.com/luporl updated https://github.com/llvm/llvm-project/pull/217124

>From 5fd99432337075a7f901c2afd2cc1c758a72e57e Mon Sep 17 00:00:00 2001
From: Leandro Lupori <leandro.lupori at linaro.org>
Date: Tue, 18 Aug 2026 17:20:47 -0300
Subject: [PATCH] [flang][OpenMP] Allow 0 after directive sentinels

Fixes #199877
---
 flang/lib/Parser/prescan.cpp                  | 16 +++++++++-------
 flang/test/Parser/OpenMP/compiler-directive.f |  7 +++++++
 2 files changed, 16 insertions(+), 7 deletions(-)
 create mode 100644 flang/test/Parser/OpenMP/compiler-directive.f

diff --git a/flang/lib/Parser/prescan.cpp b/flang/lib/Parser/prescan.cpp
index 262954d32f266..8aa3a8b2a9096 100644
--- a/flang/lib/Parser/prescan.cpp
+++ b/flang/lib/Parser/prescan.cpp
@@ -196,19 +196,21 @@ void Prescanner::Statement() {
       }
       tokens.CloseToken();
       SkipSpaces();
-      if (InConditionalLine() && inFixedForm_ && !tabInCurrentLine_ &&
-          column_ == 6 && *at_ != '\n') {
-        // !$   0   - turn '0' into a space
-        // !$   1   - turn '1' into '&'
+      if ((InConditionalLine() || IsOpenMPDirective()) && inFixedForm_ &&
+          !tabInCurrentLine_ && column_ == 6 && *at_ != '\n') {
         if (int n{IsSpace(at_)}; n || *at_ == '0') {
+          // !$   0   - turn '0' into a space
           at_ += n ? n : 1;
-        } else {
+          ++column_;
+          SkipSpaces();
+        } else if (InConditionalLine()) {
+          // !$   1   - turn '1' into '&'
           ++at_;
           EmitChar(tokens, '&');
           tokens.CloseToken();
+          ++column_;
+          SkipSpaces();
         }
-        ++column_;
-        SkipSpaces();
       }
     }
     break;
diff --git a/flang/test/Parser/OpenMP/compiler-directive.f b/flang/test/Parser/OpenMP/compiler-directive.f
new file mode 100644
index 0000000000000..eaea3805b8a58
--- /dev/null
+++ b/flang/test/Parser/OpenMP/compiler-directive.f
@@ -0,0 +1,7 @@
+! RUN: %flang_fc1 -fopenmp -fdebug-unparse %s 2>&1 | FileCheck %s
+
+! CHECK: !$OMP PARALLEL
+! CHECK: !$OMP END PARALLEL
+c$omp0parallel
+c$omp0endparallel
+      end