[flang-commits] [flang] [flang][OpenMP][Semantics] improve semantic checks for array sections (PR #132230)
Tom Eccles via flang-commits
flang-commits at lists.llvm.org
Thu Mar 20 09:57:45 PDT 2025
https://github.com/tblah updated https://github.com/llvm/llvm-project/pull/132230
>From 666e0960f1bc0f7e5d1a0afff9aa91ca9ba74c29 Mon Sep 17 00:00:00 2001
From: Tom Eccles <tom.eccles at arm.com>
Date: Thu, 20 Mar 2025 14:50:29 +0000
Subject: [PATCH 1/2] [flang][OpenMP][Semantics] improve semantic checks for
array sections
I'm not sure why strides were not allowed in array sections: the stride
is explicitly allowed by the standard from the first version where array
sections were introduced. The limitation is that the stride must not be
negative.
Here I have added the check for a negative stride and updated the test
for a zero length section to take account of the stride.
---
flang/lib/Semantics/check-omp-structure.cpp | 45 +++++++++++++--------
flang/test/Semantics/OpenMP/depend01.f90 | 11 ++++-
2 files changed, 38 insertions(+), 18 deletions(-)
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 9c9d666b5e8d5..57de3de8b8ef7 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -5304,27 +5304,40 @@ void OmpStructureChecker::CheckArraySection(
if (const auto *triplet{
std::get_if<parser::SubscriptTriplet>(&subscript.u)}) {
if (std::get<0>(triplet->t) && std::get<1>(triplet->t)) {
+ std::optional<int64_t> strideVal{std::nullopt};
+ if (std::get<2>(triplet->t)) {
+ const auto &strideExpr{std::get<2>(triplet->t)};
+ if (strideExpr) {
+ // OpenMP 6.0 Section 5.2.5: Array Sections
+ // Restrictions: if a stride expression is specified it must be
+ // positive. A stride of 0 doesn't make sense.
+ strideVal = GetIntValue(strideExpr);
+ if (strideVal && *strideVal < 1) {
+ context_.Say(GetContext().clauseSource,
+ "'%s' in %s clause must have a positive stride"_err_en_US,
+ name.ToString(),
+ parser::ToUpperCaseLetters(getClauseName(clause).str()));
+ }
+ }
+ }
const auto &lower{std::get<0>(triplet->t)};
const auto &upper{std::get<1>(triplet->t)};
if (lower && upper) {
const auto lval{GetIntValue(lower)};
const auto uval{GetIntValue(upper)};
- if (lval && uval && *uval < *lval) {
- context_.Say(GetContext().clauseSource,
- "'%s' in %s clause"
- " is a zero size array section"_err_en_US,
- name.ToString(),
- parser::ToUpperCaseLetters(getClauseName(clause).str()));
- break;
- } else if (std::get<2>(triplet->t)) {
- const auto &strideExpr{std::get<2>(triplet->t)};
- if (strideExpr) {
- if (clause == llvm::omp::Clause::OMPC_depend) {
- context_.Say(GetContext().clauseSource,
- "Stride should not be specified for array section in "
- "DEPEND "
- "clause"_err_en_US);
- }
+ if (lval && uval) {
+ int64_t sectionLen = *uval - *lval;
+ if (strideVal) {
+ sectionLen = sectionLen / *strideVal;
+ }
+
+ if (sectionLen < 1) {
+ context_.Say(GetContext().clauseSource,
+ "'%s' in %s clause"
+ " is a zero size array section"_err_en_US,
+ name.ToString(),
+ parser::ToUpperCaseLetters(getClauseName(clause).str()));
+ break;
}
}
}
diff --git a/flang/test/Semantics/OpenMP/depend01.f90 b/flang/test/Semantics/OpenMP/depend01.f90
index 29468f4358855..19fcfbf64bebd 100644
--- a/flang/test/Semantics/OpenMP/depend01.f90
+++ b/flang/test/Semantics/OpenMP/depend01.f90
@@ -17,8 +17,15 @@ program omp_depend
a(2:1) = b(2, 2)
!$omp end task
- !ERROR: Stride should not be specified for array section in DEPEND clause
- !$omp task shared(x) depend(in: a(5:10:1))
+ !ERROR: 'a' in DEPEND clause must have a positive stride
+ !ERROR: 'b' in DEPEND clause must have a positive stride
+ !ERROR: 'b' in DEPEND clause is a zero size array section
+ !$omp task shared(x) depend(in: a(10:5:-1)) depend(in: b(5:10:-1))
+ print *, a(5:10), b
+ !$omp end task
+
+ !ERROR: 'a' in DEPEND clause is a zero size array section
+ !$omp task shared(x) depend(in: a(1:5:10))
print *, a(5:10), b
!$omp end task
>From 52c542d6c2ec5714ccf7f203eead58c1605405eb Mon Sep 17 00:00:00 2001
From: Tom Eccles <tom.eccles at arm.com>
Date: Thu, 20 Mar 2025 16:56:17 +0000
Subject: [PATCH 2/2] Simplify if statements
---
flang/lib/Semantics/check-omp-structure.cpp | 23 +++++++++------------
1 file changed, 10 insertions(+), 13 deletions(-)
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 57de3de8b8ef7..ab38a95a38871 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -5305,19 +5305,16 @@ void OmpStructureChecker::CheckArraySection(
std::get_if<parser::SubscriptTriplet>(&subscript.u)}) {
if (std::get<0>(triplet->t) && std::get<1>(triplet->t)) {
std::optional<int64_t> strideVal{std::nullopt};
- if (std::get<2>(triplet->t)) {
- const auto &strideExpr{std::get<2>(triplet->t)};
- if (strideExpr) {
- // OpenMP 6.0 Section 5.2.5: Array Sections
- // Restrictions: if a stride expression is specified it must be
- // positive. A stride of 0 doesn't make sense.
- strideVal = GetIntValue(strideExpr);
- if (strideVal && *strideVal < 1) {
- context_.Say(GetContext().clauseSource,
- "'%s' in %s clause must have a positive stride"_err_en_US,
- name.ToString(),
- parser::ToUpperCaseLetters(getClauseName(clause).str()));
- }
+ if (const auto &strideExpr = std::get<2>(triplet->t)) {
+ // OpenMP 6.0 Section 5.2.5: Array Sections
+ // Restrictions: if a stride expression is specified it must be
+ // positive. A stride of 0 doesn't make sense.
+ strideVal = GetIntValue(strideExpr);
+ if (strideVal && *strideVal < 1) {
+ context_.Say(GetContext().clauseSource,
+ "'%s' in %s clause must have a positive stride"_err_en_US,
+ name.ToString(),
+ parser::ToUpperCaseLetters(getClauseName(clause).str()));
}
}
const auto &lower{std::get<0>(triplet->t)};
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