Skip compiler directives between OMP PARALLEL DO and the loop #81021
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This fixes a compilation error when code like this is presented to the
compiler:
!$OMP PARALLEL DO
!DIR$ VECTOR ALIGNED
DO 20 i=1,N
a = a + 0.5
20 CONTINUE
The directive itself is later ignored (with a warning that this is
happening), but because the compiler already errored out before that
point, it completely fails to compile this code. Other compilers
accept the code without complaints.
llvmbot
added
flang
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@llvm/pr-subscribers-flang-openmp @llvm/pr-subscribers-flang-semantics Author: Mats Petersson (Leporacanthicus) ChangesThis fixes a compilation error when code like this is presented to the compiler: !$OMP PARALLEL DO The directive itself is later ignored (with a warning that this is happening), but because the compiler already errored out before that point, it completely fails to compile this code. Other compilers accept the code without complaints. Full diff: https://github.com/llvm/llvm-project/pull/81021.diff 2 Files Affected:
diff --git a/flang/lib/Semantics/canonicalize-omp.cpp b/flang/lib/Semantics/canonicalize-omp.cpp
index 013fb408214eef..01adcf53728424 100644
--- a/flang/lib/Semantics/canonicalize-omp.cpp
+++ b/flang/lib/Semantics/canonicalize-omp.cpp
@@ -90,7 +90,11 @@ class CanonicalizationOfOmp {
auto &dir{std::get<parser::OmpLoopDirective>(beginDir.t)};
nextIt = it;
- if (++nextIt != block.end()) {
+ while (++nextIt != block.end()) {
+ // Ignore compiler directives.
+ if (auto *directive{GetConstructIf<parser::CompilerDirective>(*nextIt)})
+ continue;
+
if (auto *doCons{GetConstructIf<parser::DoConstruct>(*nextIt)}) {
if (doCons->GetLoopControl()) {
// move DoConstruct
@@ -111,12 +115,14 @@ class CanonicalizationOfOmp {
"DO loop after the %s directive must have loop control"_err_en_US,
parser::ToUpperCaseLetters(dir.source.ToString()));
}
- return; // found do-loop
+ } else {
+ messages_.Say(dir.source,
+ "A DO loop must follow the %s directive"_err_en_US,
+ parser::ToUpperCaseLetters(dir.source.ToString()));
}
+ // If we get here, we either found a loop, or issued an error message.
+ return;
}
- messages_.Say(dir.source,
- "A DO loop must follow the %s directive"_err_en_US,
- parser::ToUpperCaseLetters(dir.source.ToString()));
}
void RewriteOmpAllocations(parser::ExecutionPart &body) {
diff --git a/flang/test/Semantics/OpenMP/loop-association.f90 b/flang/test/Semantics/OpenMP/loop-association.f90
index 8a28fd8878f496..29fca3b4be5902 100644
--- a/flang/test/Semantics/OpenMP/loop-association.f90
+++ b/flang/test/Semantics/OpenMP/loop-association.f90
@@ -30,6 +30,13 @@
c = c - 1
END DO outer
+ ! Accept directives between parallel do and actual loop.
+ !$OMP PARALLEL DO
+ !DIR$ VECTOR ALIGNED
+ DO 20 i=1,N
+ a = a + 0.5
+20 CONTINUE
+
c = 16
!ERROR: DO loop after the PARALLEL DO directive must have loop control
!$omp parallel do
|
| DO 20 i=1,N | ||
| a = a + 0.5 | ||
| 20 CONTINUE | ||
|
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nit: I think this needs an !$OMP END PARALLEL DO to be valid openmp
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For the worksharing loop directives, the closing END directive is optional. However, I agree with the nit and we should have as a matter of style.
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I didn't add it, because it wasn't in the other tests that do similar loops. But I agree, it's nicer to have, so I have added it now.
| if (++nextIt != block.end()) { | ||
| while (++nextIt != block.end()) { | ||
| // Ignore compiler directives. | ||
| if (auto *directive{GetConstructIf<parser::CompilerDirective>(*nextIt)}) |
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I'm getting a warning on this line because the variable directive isn't used. And since I have -Werror set, my build fails.
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Apologies for that. Neither my GCC nor my Clang builds that I run warned for this - Trivial fix here:
This fixes a compilation error when code like this is presented to the compiler:
!$OMP PARALLEL DO
!DIR$ VECTOR ALIGNED
DO 20 i=1,N
a = a + 0.5
20 CONTINUE
The directive itself is later ignored (with a warning that this is happening), but because the compiler already errored out before that point, it completely fails to compile this code. Other compilers accept the code without complaints.