[llvm-branch-commits] [flang] [flang] Detect loops whose branching is confined to their body (PR #225757)
Kareem Ergawy via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Thu Sep 24 01:59:54 PDT 2026
https://github.com/ergawy updated https://github.com/llvm/llvm-project/pull/225757
>From 4e323a69815056d56fb287b136ab008dee54f3db Mon Sep 17 00:00:00 2001
From: ergawy <kareem.ergawy at gmail.com>
Date: Mon, 21 Sep 2026 06:16:09 -0700
Subject: [PATCH] [flang] Detect loops whose branching is confined to their
body
A DO loop is classified as either structured or unstructured, and a single
raw branch anywhere in its body forces the loop -- and every construct
enclosing it -- onto the unstructured path.
That is stronger than necessary. A loop keeps its structured control flow
as long as its branching neither leaves its body nor enters it from
outside. Classify such a loop separately from a fully unstructured one.
This only classifies: lowering is unchanged. PFT dumps mark the new
classification with '~', which is what the tests key on.
---
flang/include/flang/Lower/PFTBuilder.h | 57 ++++-
flang/lib/Lower/PFTBuilder.cpp | 214 ++++++++++++++++--
.../pre-fir-tree-unstructured-internals.f90 | 137 +++++++++++
flang/test/Lower/trailing-cycle.f90 | 15 +-
4 files changed, 388 insertions(+), 35 deletions(-)
create mode 100644 flang/test/Lower/pre-fir-tree-unstructured-internals.f90
diff --git a/flang/include/flang/Lower/PFTBuilder.h b/flang/include/flang/Lower/PFTBuilder.h
index 7e748ae554a20..930214244c74c 100644
--- a/flang/include/flang/Lower/PFTBuilder.h
+++ b/flang/include/flang/Lower/PFTBuilder.h
@@ -28,6 +28,7 @@
#include "flang/Semantics/symbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
namespace Fortran::lower::pft {
@@ -322,6 +323,50 @@ struct Evaluation : EvaluationVariant {
/// Return the FunctionLikeUnit containing this evaluation (or nullptr).
FunctionLikeUnit *getOwningProcedure() const;
+ /// How this evaluation's control flow is lowered. Ordered by how much it
+ /// constrains lowering so that classification can only strengthen; see
+ /// markControlFlow.
+ enum class ControlFlow {
+ /// Lowered structurally
+ Structured,
+ /// Lowered structurally, but the body holds unstructured control flow
+ /// confined to it. Lowering folds that body -- not the construct, and not
+ /// the loop control -- into a parent region, so the structured op's
+ /// single-block region stays well formed.
+ ///
+ /// For now, this only applies to DO constructs.
+ StructuredWithUnstructuredInternals,
+ /// Lowered as raw CFG blocks.
+ Unstructured,
+ };
+
+ /// Strengthen the classification to \p kind; it never weakens. This is what
+ /// makes the analysis order-independent: a construct marked Unstructured by
+ /// any one child stays Unstructured whatever its siblings contribute.
+ void markControlFlow(ControlFlow kind) {
+ controlFlow = std::max(controlFlow, kind);
+ }
+
+ void markUnstructured() { markControlFlow(ControlFlow::Unstructured); }
+
+ /// Lower the classification to \p kind. Only for an analysis that has proven
+ /// a stronger classification unnecessary; every other caller wants
+ /// markControlFlow, which never weakens.
+ void weakenControlFlow(ControlFlow kind) {
+ controlFlow = std::min(controlFlow, kind);
+ }
+
+ /// True when control flow is not fully structured, category (c) included.
+ /// Existing consumers ask this to decide whether raw blocks are needed, and
+ /// a category (c) construct still needs them until its body is wrapped, so
+ /// it must answer true here. Use hasUnstructuredInternals() to single out
+ /// category (c) itself.
+ bool isUnstructured() const { return controlFlow != ControlFlow::Structured; }
+
+ bool hasUnstructuredInternals() const {
+ return controlFlow == ControlFlow::StructuredWithUnstructuredInternals;
+ }
+
bool lowerAsStructured() const;
bool lowerAsUnstructured() const;
bool forceAsUnstructured() const;
@@ -339,11 +384,11 @@ struct Evaluation : EvaluationVariant {
// from anywhere within the construct.
//
// An unstructured construct is one that contains some form of goto. This
- // is indicated by the isUnstructured member flag, which may be set on a
- // statement and propagated to enclosing constructs. This distinction allows
- // a structured IF or DO statement to be materialized with custom structured
- // FIR operations. An unstructured statement is materialized as mlir
- // operation sequences that include explicit branches.
+ // is indicated by the controlFlow member, which may be set on a statement and
+ // propagated to enclosing constructs. This distinction allows a structured IF
+ // or DO statement to be materialized with custom structured FIR operations.
+ // An unstructured statement is materialized as mlir operation sequences that
+ // include explicit branches.
//
// The block member is set for statements that begin a new block. This
// block is the target of any branch to the statement. Statements may have
@@ -374,7 +419,7 @@ struct Evaluation : EvaluationVariant {
llvm::SmallVector<Evaluation *, 0> extraControlSuccessors;
Evaluation *constructExit{nullptr}; // set for constructs
bool isNewBlock{false}; // evaluation begins a new basic block
- bool isUnstructured{false}; // evaluation has unstructured control flow
+ ControlFlow controlFlow{ControlFlow::Structured};
bool negateCondition{false}; // If[Then]Stmt condition must be negated
bool activeConstruct{false}; // temporarily set for some constructs
// The enclosing evaluation-list traversal should skip this evaluation once
diff --git a/flang/lib/Lower/PFTBuilder.cpp b/flang/lib/Lower/PFTBuilder.cpp
index e6a4d11904679..948589a11b7d7 100644
--- a/flang/lib/Lower/PFTBuilder.cpp
+++ b/flang/lib/Lower/PFTBuilder.cpp
@@ -34,6 +34,9 @@ llvm::cl::opt<bool> wrapUnstructuredConstructsInExecuteRegion(
using namespace Fortran;
+static void detectStructuredWithUnstructuredInternals(
+ Fortran::lower::pft::FunctionLikeUnit &unit);
+
namespace {
static llvm::cl::opt<bool> lowerDoWhileToSCFWhile(
"lower-do-while-to-scf-while", llvm::cl::init(false),
@@ -525,11 +528,16 @@ class PFTBuilder {
}
void exitFunction() {
+ lower::pft::FunctionLikeUnit *exitingUnit = currentFunctionUnit;
currentFunctionUnit = nullptr; // Clear when exiting function
rewriteIfGotos();
endFunctionBody();
analyzeBranches(nullptr, *evaluationListStack.back()); // add branch links
+ // Branch analysis is complete, so the incoming-branch map is too.
+ if (exitingUnit)
+ detectStructuredWithUnstructuredInternals(*exitingUnit);
+
processEntryPoints();
containsStmtStack.pop_back();
popEvaluationList();
@@ -862,7 +870,7 @@ class PFTBuilder {
if (const auto *expr = std::get_if<parser::Expr>(&format.u)) {
if (semantics::ExprHasTypeCategory(*semantics::GetExpr(*expr),
common::TypeCategory::Integer))
- eval.isUnstructured = true;
+ eval.markUnstructured();
}
};
auto analyzeSpecs{[&](const auto &specList) {
@@ -916,7 +924,7 @@ class PFTBuilder {
/// Mark the target of a branch as a new block.
void markBranchTarget(lower::pft::Evaluation &sourceEvaluation,
lower::pft::Evaluation &targetEvaluation) {
- sourceEvaluation.isUnstructured = true;
+ sourceEvaluation.markUnstructured();
if (!sourceEvaluation.controlSuccessor)
sourceEvaluation.controlSuccessor = &targetEvaluation;
else if (sourceEvaluation.controlSuccessor != &targetEvaluation &&
@@ -942,11 +950,11 @@ class PFTBuilder {
if (sourceConstruct != targetConstruct) // branch into a construct body
for (lower::pft::Evaluation *eval = &targetEvaluation; eval;
eval = eval->parentConstruct) {
- eval->isUnstructured = true;
+ eval->markUnstructured();
// If the branch is a backward branch into an already analyzed
// DO or IF construct, mark the construct exit as a new block.
- // For a forward branch, the isUnstructured flag will cause this
- // to be done when the construct is analyzed.
+ // For a forward branch, the Unstructured classification will cause
+ // this to be done when the construct is analyzed.
if (eval->constructExit && (eval->isA<parser::DoConstruct>() ||
eval->isA<parser::IfConstruct>()))
eval->constructExit->isNewBlock = true;
@@ -1051,7 +1059,7 @@ class PFTBuilder {
markBranchTarget(eval, *construct->constructExit);
},
[&](const parser::FailImageStmt &) {
- eval.isUnstructured = true;
+ eval.markUnstructured();
if (eval.lexicalSuccessor->lexicalSuccessor)
markSuccessorAsNewBlock(eval);
},
@@ -1061,12 +1069,12 @@ class PFTBuilder {
lastConstructStmtEvaluation = &eval;
},
[&](const parser::ReturnStmt &) {
- eval.isUnstructured = true;
+ eval.markUnstructured();
if (eval.lexicalSuccessor->lexicalSuccessor)
markSuccessorAsNewBlock(eval);
},
[&](const parser::StopStmt &) {
- eval.isUnstructured = true;
+ eval.markUnstructured();
if (eval.lexicalSuccessor->lexicalSuccessor)
markSuccessorAsNewBlock(eval);
},
@@ -1094,7 +1102,7 @@ class PFTBuilder {
target->isNewBlock = true;
for (lower::pft::Evaluation *parent = target->parentConstruct;
parent; parent = parent->parentConstruct) {
- parent->isUnstructured = true;
+ parent->markUnstructured();
// The exit of an enclosing DO or IF construct is a new block.
if (parent->constructExit &&
(parent->isA<parser::DoConstruct>() ||
@@ -1140,7 +1148,7 @@ class PFTBuilder {
for (auto label : iter->second)
markIfBranchTarget(label);
}
- eval.isUnstructured = true;
+ eval.markUnstructured();
markSuccessorAsNewBlock(eval);
},
@@ -1181,7 +1189,7 @@ class PFTBuilder {
const auto &loopControl =
std::get<std::optional<parser::LoopControl>>(s.t);
if (!loopControl.has_value()) {
- eval.isUnstructured = true; // infinite loop
+ eval.markUnstructured(); // infinite loop
return;
}
eval.nonNopSuccessor().isNewBlock = true;
@@ -1190,13 +1198,13 @@ class PFTBuilder {
std::get_if<parser::LoopControl::Bounds>(&loopControl->u)) {
if (bounds->Name().thing.symbol->GetType()->IsNumeric(
common::TypeCategory::Real))
- eval.isUnstructured = true; // real-valued loop control
+ eval.markUnstructured(); // real-valued loop control
} else if (std::get_if<parser::ScalarLogicalExpr>(
&loopControl->u)) {
// Leave DO WHILE structured when -lower-do-while-to-scf-while is
// enabled; branch analysis will mark unstructured cases.
if (!lowerDoWhileToSCFWhile)
- eval.isUnstructured = true; // while loop
+ eval.markUnstructured(); // while loop
}
},
[&](const parser::EndDoStmt &) {
@@ -1277,7 +1285,7 @@ class PFTBuilder {
},
[&](const parser::CaseConstruct &) {
eval.constructExit = &eval.evaluationList->back();
- eval.isUnstructured = true;
+ eval.markUnstructured();
},
[&](const parser::ChangeTeamConstruct &) {
eval.constructExit = &eval.evaluationList->back();
@@ -1290,11 +1298,11 @@ class PFTBuilder {
[&](const parser::IfConstruct &) { setConstructExit(eval); },
[&](const parser::SelectRankConstruct &) {
eval.constructExit = &eval.evaluationList->back();
- eval.isUnstructured = true;
+ eval.markUnstructured();
},
[&](const parser::SelectTypeConstruct &) {
eval.constructExit = &eval.evaluationList->back();
- eval.isUnstructured = true;
+ eval.markUnstructured();
},
[&](const parser::WhereConstruct &) { setConstructExit(eval); },
@@ -1315,12 +1323,12 @@ class PFTBuilder {
if (eval.evaluationList)
analyzeBranches(&eval, *eval.evaluationList);
- // Propagate isUnstructured flag to enclosing construct -- unless the
- // wrap pass will fold this construct into a self-contained
+ // Propagate the Unstructured classification to the enclosing construct --
+ // unless the wrap pass will fold this construct into a self-contained
// scf.execute_region, in which case the parent sees only a single op.
- if (parentConstruct && eval.isUnstructured &&
+ if (parentConstruct && eval.isUnstructured() &&
!lower::pft::isWrappableConstruct(eval, semanticsContext))
- parentConstruct->isUnstructured = true;
+ parentConstruct->markUnstructured();
// The successor of a branch starts a new block.
if (eval.controlSuccessor && eval.isActionStmt() &&
@@ -1472,7 +1480,11 @@ class PFTDumper {
const std::string &indentString, int indent = 1) {
llvm::StringRef name = evaluationName(eval);
llvm::StringRef newBlock = eval.isNewBlock ? "^" : "";
- llvm::StringRef bang = eval.isUnstructured ? "!" : "";
+ // "!" marks an unstructured evaluation. "~" marks one that is structured
+ // on the outside but has unstructured internals.
+ llvm::StringRef bang = eval.hasUnstructuredInternals()
+ ? "~"
+ : (eval.isUnstructured() ? "!" : "");
outputStream << indentString;
if (eval.printIndex)
outputStream << eval.printIndex << ' ';
@@ -1720,7 +1732,7 @@ bool Fortran::lower::pft::Evaluation::lowerAsStructured() const {
}
bool Fortran::lower::pft::Evaluation::lowerAsUnstructured() const {
- return isUnstructured || clDisableStructuredFir;
+ return isUnstructured() || clDisableStructuredFir;
}
bool Fortran::lower::pft::Evaluation::forceAsUnstructured() const {
@@ -2750,13 +2762,169 @@ static bool isOmpLoopBody(const Fortran::lower::pft::Evaluation &eval,
return isAssociatedLoop(chain, loop->GetNestedLoop(), n);
}
+/// The evaluations forming a loop's body: everything between the loop control
+/// statements, which bracket it and are lowered outside any body wrap.
+static llvm::iterator_range<Fortran::lower::pft::EvaluationList::const_iterator>
+loopBodyRange(const Fortran::lower::pft::Evaluation &loop) {
+ const auto &list = *loop.evaluationList;
+ return llvm::make_range(std::next(list.begin()), std::prev(list.end()));
+}
+
+/// True when \p eval lies in \p loop's body rather than in its loop control.
+static bool isInLoopBody(const Fortran::lower::pft::Evaluation *eval,
+ const Fortran::lower::pft::Evaluation &loop) {
+ if (!eval || !loop.evaluationList || loop.evaluationList->empty())
+ return false;
+ const Fortran::lower::pft::Evaluation *first = &loop.evaluationList->front();
+ const Fortran::lower::pft::Evaluation *last = &loop.evaluationList->back();
+ for (const Fortran::lower::pft::Evaluation *p = eval; p;
+ p = p->parentConstruct)
+ if (p->parentConstruct == &loop)
+ return p != first && p != last;
+ return false;
+}
+
+/// A loop that can be lowered structurally even though its body holds
+/// unstructured control flow, because that control flow is confined to the body
+/// and can be folded into an SESE region.
+///
+/// The loop qualifies when:
+/// 1. every branch leaving its body lands back inside that body, and
+/// 2. every branch into its body comes from inside that body,
+/// and the body holds nothing a region cannot accommodate: an infinite DO
+/// never reaches the region's yield so RegionDCE would drop it, a ReturnStmt
+/// builds the function's final block in the current region, and a listless
+/// assigned GO TO has targets that cannot be enumerated -- so condition 1
+/// cannot be decided at all rather than merely failing.
+///
+/// A CYCLE is not an escape: its target is the EndDoStmt, which is where the
+/// wrap's yield sits, so it lands on the boundary. An EXIT targets the
+/// construct exit, beyond the loop entirely, and does escape.
+static bool isStructurableWithUnstructuredInternals(
+ const Fortran::lower::pft::Evaluation &loop,
+ const Fortran::lower::pft::FunctionLikeUnit &unit) {
+
+ if (!loop.isUnstructured() || !loop.evaluationList ||
+ loop.evaluationList->size() < 3)
+ return false;
+
+ // Only an increment loop keeps all of its control outside the body. A DO
+ // WHILE or an infinite DO lowers through a header block and a back edge, and
+ // a do concurrent has no plain bounds triple either, so in each case the
+ // loop's own control flow runs through the body a wrap would cover.
+ const auto *doConstruct = loop.getIf<parser::DoConstruct>();
+ if (!doConstruct)
+ return false;
+
+ const auto &loopControl = doConstruct->GetLoopControl();
+ if (!loopControl)
+ return false;
+
+ const auto *bounds =
+ std::get_if<parser::LoopControl::Bounds>(&loopControl->u);
+ if (!bounds)
+ return false;
+
+ // A REAL control variable does not lower to fir.do_loop, whose induction
+ // variable must be a signless integer or index, so such a loop is lowered as
+ // raw CFG whatever its body looks like.
+ const semantics::Symbol *ctrlVar = bounds->Name().thing.symbol;
+ if (!ctrlVar)
+ return false;
+
+ const semantics::DeclTypeSpec *ctrlType = ctrlVar->GetType();
+ if (!ctrlType || ctrlType->category() != semantics::DeclTypeSpec::Numeric ||
+ ctrlType->numericTypeSpec().category() != common::TypeCategory::Integer)
+ return false;
+
+ const Fortran::lower::pft::Evaluation *endDoStmt =
+ &loop.evaluationList->back();
+
+ auto isInfiniteDo = [](const parser::DoConstruct *d) {
+ return d && !d->GetLoopControl().has_value();
+ };
+
+ auto targetEscapes = [&](const Fortran::lower::pft::Evaluation *target) {
+ return target != endDoStmt && !isInLoopBody(target, loop);
+ };
+
+ std::function<bool(const Fortran::lower::pft::Evaluation &)> check =
+ [&](const Fortran::lower::pft::Evaluation &e) -> bool {
+ if (e.isA<parser::ReturnStmt>() ||
+ isInfiniteDo(e.getIf<parser::DoConstruct>()))
+ return false;
+
+ if (const auto *g = e.getIf<parser::AssignedGotoStmt>())
+ if (std::get<std::list<parser::Label>>(g->t).empty())
+ return false;
+
+ // Condition 1: nothing leaves the body, CYCLE excepted.
+ if (e.controlSuccessor && targetEscapes(e.controlSuccessor))
+ return false;
+
+ for (const Fortran::lower::pft::Evaluation *extra :
+ e.extraControlSuccessors)
+ if (targetEscapes(extra))
+ return false;
+
+ // Condition 2: nothing enters the body from outside it. This is the
+ // lookup the incoming-branch map exists for.
+ auto it = unit.incomingBranches.find(&e);
+ if (it != unit.incomingBranches.end())
+ for (const Fortran::lower::pft::Evaluation *src : it->second)
+ if (!isInLoopBody(src, loop))
+ return false;
+
+ if (e.evaluationList)
+ for (const Fortran::lower::pft::Evaluation &nested : *e.evaluationList)
+ if (!check(nested))
+ return false;
+
+ return true;
+ };
+
+ for (const Fortran::lower::pft::Evaluation &e : loopBodyRange(loop))
+ if (!check(e))
+ return false;
+
+ return true;
+}
+
+/// Reclassify every qualifying loop in \p unit.
+///
+/// Runs after branch analysis, when the incoming-branch map is complete;
+/// during analysis a branch later in the function would not yet be recorded
+/// and condition 2 would read a partial map.
+///
+/// Ancestors are deliberately left alone. A loop reclassified here lowers to a
+/// structured op, and a structured op is legal inside a parent being lowered
+/// as raw CFG, so leaving the parent Unstructured is conservative but correct.
+static void detectStructuredWithUnstructuredInternals(
+ Fortran::lower::pft::FunctionLikeUnit &unit) {
+ std::function<void(Fortran::lower::pft::EvaluationList &)> visit =
+ [&](Fortran::lower::pft::EvaluationList &list) {
+ for (Fortran::lower::pft::Evaluation &e : list) {
+ if (e.evaluationList)
+ visit(*e.evaluationList);
+
+ if (e.isA<parser::DoConstruct>() &&
+ isStructurableWithUnstructuredInternals(e, unit))
+ // The one place the classification weakens: detection has proven
+ // Unstructured unnecessary.
+ e.weakenControlFlow(Fortran::lower::pft::Evaluation::ControlFlow::
+ StructuredWithUnstructuredInternals);
+ }
+ };
+ visit(unit.evaluationList);
+}
+
bool Fortran::lower::pft::isWrappableConstruct(
const Fortran::lower::pft::Evaluation &eval,
const Fortran::semantics::SemanticsContext &semaCtx) {
if (!wrapUnstructuredConstructsInExecuteRegion)
return false;
- if (!eval.isUnstructured)
+ if (!eval.isUnstructured())
return false;
if (!(eval.isA<Fortran::parser::DoConstruct>() ||
diff --git a/flang/test/Lower/pre-fir-tree-unstructured-internals.f90 b/flang/test/Lower/pre-fir-tree-unstructured-internals.f90
new file mode 100644
index 0000000000000..30236e51bb40b
--- /dev/null
+++ b/flang/test/Lower/pre-fir-tree-unstructured-internals.f90
@@ -0,0 +1,137 @@
+! RUN: %flang_fc1 -fdebug-dump-pft %s 2>&1 | FileCheck %s
+
+! Detection of loops whose control flow is structured on the outside but has
+! raw branching confined to the body. Such a loop is marked '~' in the dump, as
+! opposed to '!' for a fully unstructured one and no marker for a structured
+! one.
+
+! Two forward GOTOs that both land inside the body. Nothing enters the body
+! from outside and nothing leaves it, so the loop qualifies even though its
+! internals are branch-based.
+subroutine internal_gotos(a, n)
+ real :: a(n)
+ ! CHECK: <<DoConstruct~>> -> 10
+ ! CHECK: 6 GotoStmt! -> 8: goto 20
+ ! CHECK: 8 ^AssignmentStmt <- 6: 20 a(i) = a(i) + 1.0
+ ! CHECK: <<End DoConstruct~>>
+ do i = 1, n
+ if (a(i) > 0.0) goto 10
+ a(i) = 1.0
+ goto 20
+10 a(i) = 2.0
+20 a(i) = a(i) + 1.0
+ end do
+end subroutine
+
+! A CYCLE targets the EndDoStmt, which is the boundary between the body and the
+! loop control, so it does not count as escaping the body.
+subroutine cycle_in_if_block(a, n)
+ real :: a(n)
+ ! CHECK: <<DoConstruct~>> -> 8
+ ! CHECK: [[CYC:[0-9]+]] CycleStmt! -> [[END:[0-9]+]]: cycle
+ ! CHECK: [[END]] ^EndDoStmt -> 1 <- [[CYC]]: end do
+ ! CHECK: <<End DoConstruct~>>
+ do i = 1, n
+ if (a(i) > 0.0) then
+ a(i) = 1.0
+ cycle
+ end if
+ a(i) = 2.0
+ end do
+end subroutine
+
+! The GOTO leaves the loop entirely, so the branch graph is not contained.
+subroutine escaping_goto(a, n)
+ real :: a(n)
+ ! CHECK: <<DoConstruct!>> -> 7
+ ! CHECK: <<End DoConstruct!>>
+ do i = 1, n
+ if (a(i) > 0.0) goto 20
+ a(i) = 2.0
+ end do
+20 continue
+end subroutine
+
+! A RETURN escapes the loop and the procedure both.
+subroutine body_has_return(a, n)
+ real :: a(n)
+ ! CHECK: <<DoConstruct!>> -> 7
+ ! CHECK: <<End DoConstruct!>>
+ do i = 1, n
+ if (a(i) > 0.0) return
+ a(i) = 3.0
+ end do
+end subroutine
+
+! The branch originates outside the loop and lands inside its body, so the body
+! has an external entry point and cannot be wrapped.
+subroutine incoming_from_outside(a, n)
+ real :: a(n)
+ ! CHECK: <<DoConstruct!>> -> 8
+ ! CHECK: <<End DoConstruct!>>
+ if (n < 0) goto 30
+ do i = 1, n
+ a(i) = 4.0
+30 continue
+ end do
+end subroutine
+
+! An inner infinite DO has no structured loop control to preserve.
+subroutine infinite_inner(a, n)
+ real :: a(n)
+ ! CHECK: <<DoConstruct!>> -> 9
+ ! CHECK: <<DoConstruct!>> -> 8
+ ! CHECK: <<End DoConstruct!>>
+ ! CHECK: <<End DoConstruct!>>
+ do i = 1, n
+ do
+ a(i) = 1.0
+ if (a(i) > 0.0) exit
+ end do
+ end do
+end subroutine
+
+! The shape that motivates this work: a forward GOTO raised inside a nested
+! IF, jumping over a whole inner DO construct and landing on the last statement
+! of the outer loop body. Both endpoints are inside the body, so the outer loop
+! is category (c) even though the branch crosses construct boundaries. Note the
+! two inner DO constructs stay structured -- only the outer loop carries the
+! branching.
+subroutine goto_over_inner_loop(qfx, hfx, a, its, ite, jts, jte, force, flux)
+ real :: qfx(ite,jte), hfx(ite,jte), a(ite,jte)
+ logical :: force
+ integer :: flux
+ ! CHECK: <<DoConstruct~>> -> 18
+ ! CHECK: <<DoConstruct>> -> 6
+ ! CHECK: <<End DoConstruct>>
+ ! CHECK: [[GOTO:[0-9]+]] ^GotoStmt! -> [[TGT:[0-9]+]]: goto 350
+ ! CHECK: <<DoConstruct>> -> [[TGT]]
+ ! CHECK: <<End DoConstruct>>
+ ! CHECK: [[TGT]] ^ContinueStmt <- [[GOTO]]: 350 continue
+ ! CHECK: 17 EndDoStmt -> 1: enddo
+ ! CHECK: <<End DoConstruct~>>
+ do j = jts, jte
+ do 330 i = its, ite
+ a(i,j) = a(i,j) + 1.0
+330 continue
+335 continue
+ if (force) then
+ if (flux .eq. 1) goto 350
+ endif
+ do i = its, ite
+ qfx(i,j) = 0.
+ hfx(i,j) = 0.
+ enddo
+350 continue
+ enddo
+end subroutine
+
+! No branching at all; detection must leave it unmarked.
+subroutine fully_structured(a, n)
+ real :: a(n)
+ ! CHECK: <<DoConstruct>> -> 4
+ ! CHECK: <<End DoConstruct>>
+ do i = 1, n
+ a(i) = 5.0
+ end do
+end subroutine
diff --git a/flang/test/Lower/trailing-cycle.f90 b/flang/test/Lower/trailing-cycle.f90
index 47f904cb46c99..4a69a3b4fc0ba 100644
--- a/flang/test/Lower/trailing-cycle.f90
+++ b/flang/test/Lower/trailing-cycle.f90
@@ -58,8 +58,10 @@ subroutine trailing_cycle(a, n)
end do
end do outer
- ! A labeled CYCLE may be a branch target and is kept.
- ! CHECK: <<DoConstruct!>> -> 25
+ ! A labeled CYCLE may be a branch target and is kept. Its branches stay
+ ! inside the loop body, so the loop is category (c): structured control with
+ ! unstructured internals, marked '~' rather than '!'.
+ ! CHECK: <<DoConstruct~>> -> 25
! CHECK: 18 NonLabelDoStmt -> 24: do i = 1, n
! CHECK: <<IfConstruct>> -> 23
! CHECK: 19 ^IfStmt [negate] -> 23: if(a(i) > 0.0) goto 10
@@ -68,20 +70,21 @@ subroutine trailing_cycle(a, n)
! CHECK: <<End IfConstruct>>
! CHECK: 23 CycleStmt! -> 24: 10 cycle
! CHECK: 24 ^EndDoStmt -> 18 <- 23: end do
- ! CHECK: <<End DoConstruct!>>
+ ! CHECK: <<End DoConstruct~>>
do i = 1, n
if (a(i) > 0.0) goto 10
a(i) = 4.0
10 cycle
end do
- ! A CYCLE that is not last is a real branch and is kept.
- ! CHECK: <<DoConstruct!>> -> 29
+ ! A CYCLE that is not last is a real branch and is kept. It targets the
+ ! EndDoStmt, which is the loop-body boundary, so this is category (c) too.
+ ! CHECK: <<DoConstruct~>> -> 29
! CHECK: 25 ^NonLabelDoStmt -> 28: do i = 1, n
! CHECK: 26 ^CycleStmt! -> 28: cycle
! CHECK: 27 ^AssignmentStmt: a(i) = 5.0
! CHECK: 28 ^EndDoStmt -> 25 <- 26: end do
- ! CHECK: <<End DoConstruct!>>
+ ! CHECK: <<End DoConstruct~>>
do i = 1, n
cycle
a(i) = 5.0
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