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Improve resolution and compilation of control flow loops and labels #4522

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46 changes: 46 additions & 0 deletions gcc/rust/backend/rust-compile-context.h
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Expand Up @@ -266,6 +266,34 @@ class Context
return true;
}

void insert_break_label (HirId id, tree label)
{
compiled_break_labels[id] = label;
}

bool lookup_break_label (HirId id, tree *label)

@P-E-P P-E-P May 24, 2026

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Even if the old API uses an out pointer with a bool return value most of the new APIs try to use optional when available.

{
auto it = compiled_break_labels.find (id);
if (it == compiled_break_labels.end ())
return false;
*label = it->second;
return true;
}

void insert_continue_label (HirId id, tree label)
{
compiled_continue_labels[id] = label;
}

bool lookup_continue_label (HirId id, tree *label)

@P-E-P P-E-P May 24, 2026

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Likewise.

{
auto it = compiled_continue_labels.find (id);
if (it == compiled_continue_labels.end ())
return false;
*label = it->second;
return true;
}

void insert_pattern_binding (HirId id, tree binding)
{
implicit_pattern_bindings[id] = binding;
Expand Down Expand Up @@ -355,6 +383,21 @@ class Context
return pop;
}

void push_loop_end_label (tree label) { loop_end_labels.push_back (label); }

tree peek_loop_end_label ()
{
rust_assert (!loop_end_labels.empty ());
return loop_end_labels.back ();
}

tree pop_loop_end_label ()
{
tree pop = loop_end_labels.back ();
loop_end_labels.pop_back ();
return pop;
}

void push_const_context (void) { const_context++; }
void pop_const_context (void)
{
Expand Down Expand Up @@ -417,10 +460,13 @@ class Context
std::map<HirId, tree> compiled_fn_map;
std::map<HirId, tree> compiled_consts;
std::map<HirId, tree> compiled_labels;
std::map<HirId, tree> compiled_break_labels;
std::map<HirId, tree> compiled_continue_labels;
std::vector<::std::vector<tree>> statements;
std::vector<tree> scope_stack;
std::vector<::Bvariable *> loop_value_stack;
std::vector<tree> loop_begin_labels;
std::vector<tree> loop_end_labels;
std::map<DefId, std::vector<std::pair<const TyTy::BaseType *, tree>>>
mono_fns;
std::map<DefId, std::vector<std::pair<const TyTy::ClosureType *, tree>>>
Expand Down
105 changes: 65 additions & 40 deletions gcc/rust/backend/rust-compile-expr.cc
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Expand Up @@ -17,6 +17,8 @@
// <http://www.gnu.org/licenses/>.

#include "rust-compile-expr.h"
#include "line-map.h"
#include "optional.h"
#include "rust-backend.h"
#include "rust-compile-type.h"
#include "rust-compile-struct-field-expr.h"
Expand Down Expand Up @@ -758,24 +760,14 @@ CompileExpr::visit (HIR::LoopExpr &expr)
ctx->add_statement (ret_var_stmt);
ctx->push_loop_context (tmp);

tl::optional<HIR::LoopLabel> loop_label = tl::nullopt;
if (expr.has_loop_label ())
{
HIR::LoopLabel &loop_label = expr.get_loop_label ();
tree label
= Backend::label (fnctx.fndecl, loop_label.get_lifetime ().get_name (),
loop_label.get_locus ());
tree label_decl = Backend::label_definition_statement (label);
ctx->add_statement (label_decl);
ctx->insert_label_decl (
loop_label.get_lifetime ().get_mappings ().get_hirid (), label);
}
loop_label = tl::optional<HIR::LoopLabel> (expr.get_loop_label ());
std::pair<tree, tree> loop_labels = construct_loop_labels (loop_label);
tree loop_begin_label = loop_labels.first;
tree loop_end_label = loop_labels.second;

tree loop_begin_label
= Backend::label (fnctx.fndecl, tl::nullopt, expr.get_locus ());
tree loop_begin_label_decl
= Backend::label_definition_statement (loop_begin_label);
ctx->add_statement (loop_begin_label_decl);
ctx->push_loop_begin_label (loop_begin_label);
ctx->add_statement (loop_begin_label);

tree code_block
= CompileBlock::compile (expr.get_loop_block (), ctx, nullptr);
Expand All @@ -784,41 +776,31 @@ CompileExpr::visit (HIR::LoopExpr &expr)

ctx->pop_loop_context ();
translated = Backend::var_expression (tmp, expr.get_locus ());

ctx->add_statement (loop_end_label);
ctx->pop_loop_begin_label ();
ctx->pop_loop_end_label ();
}

void
CompileExpr::visit (HIR::WhileLoopExpr &expr)
{
fncontext fnctx = ctx->peek_fn ();
tree enclosing_scope = ctx->peek_enclosing_scope ();
ctx->push_loop_context (nullptr);
tl::optional<HIR::LoopLabel> loop_label = tl::nullopt;
if (expr.has_loop_label ())
{
HIR::LoopLabel &loop_label = expr.get_loop_label ();
tree label
= Backend::label (fnctx.fndecl, loop_label.get_lifetime ().get_name (),
loop_label.get_locus ());
tree label_decl = Backend::label_definition_statement (label);
ctx->add_statement (label_decl);
ctx->insert_label_decl (
loop_label.get_lifetime ().get_mappings ().get_hirid (), label);
}

loop_label = tl::optional<HIR::LoopLabel> (expr.get_loop_label ());
std::pair<tree, tree> loop_labels = construct_loop_labels (loop_label);
tree loop_begin_label = loop_labels.first;
tree loop_end_label = loop_labels.second;
std::vector<Bvariable *> locals;
location_t start_location = expr.get_loop_block ().get_locus ();
location_t end_location = expr.get_loop_block ().get_locus (); // FIXME

tree enclosing_scope = ctx->peek_enclosing_scope ();
tree loop_block = Backend::block (fnctx.fndecl, enclosing_scope, locals,
start_location, end_location);
ctx->push_block (loop_block);

tree loop_begin_label
= Backend::label (fnctx.fndecl, tl::nullopt, expr.get_locus ());
tree loop_begin_label_decl
= Backend::label_definition_statement (loop_begin_label);
ctx->add_statement (loop_begin_label_decl);
ctx->push_loop_begin_label (loop_begin_label);
ctx->add_statement (loop_begin_label);

HIR::Expr &predicate = expr.get_predicate_expr ();
TyTy::BaseType *predicate_type = nullptr;
Expand Down Expand Up @@ -847,6 +829,9 @@ CompileExpr::visit (HIR::WhileLoopExpr &expr)

tree loop_expr = Backend::loop_expression (loop_block, expr.get_locus ());
ctx->add_statement (loop_expr);
ctx->add_statement (loop_end_label);
ctx->pop_loop_end_label ();

translated = unit_expression (expr.get_locus ());
}

Expand All @@ -862,6 +847,9 @@ CompileExpr::visit (HIR::BreakExpr &expr)
return;

Bvariable *loop_result_holder = ctx->peek_loop_context ();
if (loop_result_holder == nullptr)
return;

tree result_reference
= Backend::var_expression (loop_result_holder,
expr.get_expr ().get_locus ());
Expand Down Expand Up @@ -902,7 +890,7 @@ CompileExpr::visit (HIR::BreakExpr &expr)
auto ref = hid.value ();

tree label = NULL_TREE;
if (!ctx->lookup_label_decl (ref, &label))
if (!ctx->lookup_break_label (ref, &label))
{
rust_error_at (expr.get_label ().get_locus (),
"failed to lookup compiled label");
Expand All @@ -925,8 +913,7 @@ void
CompileExpr::visit (HIR::ContinueExpr &expr)
{
translated = error_mark_node;
if (!ctx->have_loop_context ())
return;
rust_assert (ctx->have_loop_context () && "continue is outside of loop");

tree label = ctx->peek_loop_begin_label ();
if (expr.has_label ())
Expand Down Expand Up @@ -958,7 +945,7 @@ CompileExpr::visit (HIR::ContinueExpr &expr)
}
auto ref = hid.value ();

if (!ctx->lookup_label_decl (ref, &label))
if (!ctx->lookup_continue_label (ref, &label))
{
rust_error_at (expr.get_label ().get_locus (),
"failed to lookup compiled label");
Expand Down Expand Up @@ -2758,5 +2745,43 @@ CompileExpr::generate_possible_fn_trait_call (HIR::CallExpr &expr,
return true;
}

std::pair<tree, tree>
CompileExpr::construct_loop_labels (tl::optional<HIR::LoopLabel> opt_loop_label)
{
fncontext fnctx = ctx->peek_fn ();
tree break_label_decl = NULL_TREE;
tree break_label_expr = NULL_TREE;
tree continue_label_decl = NULL_TREE;
tree continue_label_expr = NULL_TREE;
location_t label_locus = UNKNOWN_LOCATION;
tl::optional<std::string> continue_label_name = tl::nullopt;
tl::optional<std::string> break_label_name = tl::nullopt;
tl::optional<HirId> label_hirid = tl::nullopt;
if (opt_loop_label.has_value ())
{
label_locus = opt_loop_label.value ().get_locus ();
HIR::LoopLabel &loop_label = opt_loop_label.value ();
std::string label_name = loop_label.get_lifetime ().get_name ();
continue_label_name = label_name + "_continue";
break_label_name = label_name + "_break";
label_hirid = loop_label.get_lifetime ().get_mappings ().get_hirid ();
}
continue_label_decl
= Backend::label (fnctx.fndecl, continue_label_name, label_locus);
continue_label_expr
= Backend::label_definition_statement (continue_label_decl);
break_label_decl
= Backend::label (fnctx.fndecl, break_label_name, label_locus);
break_label_expr = Backend::label_definition_statement (break_label_decl);
if (label_hirid.has_value ())
{
ctx->insert_continue_label (label_hirid.value (), continue_label_decl);
ctx->insert_break_label (label_hirid.value (), break_label_decl);
}
ctx->push_loop_begin_label (continue_label_decl);
ctx->push_loop_end_label (break_label_decl);
return std::make_pair (continue_label_expr, break_label_expr);
}

} // namespace Compile
} // namespace Rust
4 changes: 4 additions & 0 deletions gcc/rust/backend/rust-compile-expr.h
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Expand Up @@ -19,6 +19,7 @@
#ifndef RUST_COMPILE_EXPR
#define RUST_COMPILE_EXPR

#include "optional.h"
#include "rust-compile-base.h"
#include "rust-hir-visitor.h"

Expand Down Expand Up @@ -151,6 +152,9 @@ class CompileExpr : private HIRCompileBase, protected HIR::HIRExpressionVisitor
bool generate_possible_fn_trait_call (HIR::CallExpr &expr, tree receiver,
tree *result);

std::pair<tree, tree>
construct_loop_labels (tl::optional<HIR::LoopLabel> loop_label);

private:
CompileExpr (Context *ctx);

Expand Down
20 changes: 20 additions & 0 deletions gcc/rust/resolve/rust-default-resolver.cc
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Expand Up @@ -85,6 +85,26 @@ DefaultResolver::visit (AST::Function &function)
function.get_function_name ());
}

void
DefaultResolver::visit (AST::LoopExpr &expr)
{
ctx.scoped (Rib::Kind::Normal, expr.get_node_id (),
[this, &expr] () { AST::DefaultASTVisitor::visit (expr); });
}

void
DefaultResolver::visit (AST::WhileLoopExpr &expr)
{
ctx.scoped (Rib::Kind::Normal, expr.get_node_id (),
[this, &expr] () { AST::DefaultASTVisitor::visit (expr); });
}

void
DefaultResolver::visit (AST::WhileLetLoopExpr &expr)
{
ctx.scoped (Rib::Kind::Normal, expr.get_node_id (),
[this, &expr] () { AST::DefaultASTVisitor::visit (expr); });
}
void
DefaultResolver::visit (AST::ForLoopExpr &expr)
{
Expand Down
3 changes: 3 additions & 0 deletions gcc/rust/resolve/rust-default-resolver.h
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Expand Up @@ -46,6 +46,9 @@ class DefaultResolver : public AST::DefaultASTVisitor
void visit (AST::BlockExpr &) override;
void visit (AST::Module &) override;
void visit (AST::Function &) override;
void visit (AST::LoopExpr &expr) override;
void visit (AST::WhileLoopExpr &expr) override;
void visit (AST::WhileLetLoopExpr &expr) override;
void visit (AST::ForLoopExpr &expr) override;
virtual void visit_if_let_patterns (AST::IfLetExpr &expr);
void visit (AST::IfLetExpr &expr) override;
Expand Down
9 changes: 7 additions & 2 deletions gcc/rust/resolve/rust-late-name-resolver-2.0.cc
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Expand Up @@ -300,8 +300,13 @@ void
Late::visit (AST::LoopLabel &label)
{
auto &lifetime = label.get_lifetime ();
ctx.labels.insert (Identifier (lifetime.as_string (), lifetime.get_locus ()),
lifetime.get_node_id ());
auto resolved = ctx.lookup (lifetime.get_node_id ());
if (!resolved.has_value ())
{
ctx.labels.insert (Identifier (lifetime.as_string (),
lifetime.get_locus ()),
lifetime.get_node_id ());
}
}

void
Expand Down
14 changes: 9 additions & 5 deletions gcc/rust/resolve/rust-name-resolution-context.cc
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Expand Up @@ -201,7 +201,7 @@ NameResolutionContext::insert (Identifier name, NodeId id, Namespace ns)
return macros.insert (name, id);
case Namespace::Labels:
default:
// return labels.insert (name, id);
return labels.insert (name, id);
rust_unreachable ();
}
}
Expand Down Expand Up @@ -229,8 +229,8 @@ NameResolutionContext::insert_shadowable (Identifier name, NodeId id,
case Namespace::Macros:
return macros.insert_shadowable (name, id);
case Namespace::Labels:
return labels.insert (name, id);
default:
// return labels.insert (name, id);
rust_unreachable ();
}
}
Expand All @@ -247,8 +247,8 @@ NameResolutionContext::insert_globbed (Identifier name, NodeId id, Namespace ns)
case Namespace::Macros:
return macros.insert_globbed (name, id);
case Namespace::Labels:
return labels.insert (name, id);
default:
// return labels.insert (name, id);
rust_unreachable ();
}
}
Expand Down Expand Up @@ -282,14 +282,14 @@ NameResolutionContext::scoped (Rib::Kind rib_kind, NodeId id,
values.push (rib_kind, id, path);
types.push (rib_kind, id, path);
macros.push (rib_kind, id, path);
// labels.push (rib, id);
labels.push (rib_kind, id, path);

lambda ();

values.pop ();
types.pop ();
macros.pop ();
// labels.pop (rib);
labels.pop ();
}

void
Expand All @@ -310,6 +310,8 @@ NameResolutionContext::scoped (Rib::Kind rib_kind, Namespace ns,
types.push (rib_kind, scope_id, path);
break;
case Namespace::Labels:
labels.push (rib_kind, scope_id, path);
break;
case Namespace::Macros:
gcc_unreachable ();
}
Expand All @@ -325,6 +327,8 @@ NameResolutionContext::scoped (Rib::Kind rib_kind, Namespace ns,
types.pop ();
break;
case Namespace::Labels:
labels.pop ();
break;
case Namespace::Macros:
gcc_unreachable ();
}
Expand Down
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