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[flang] Distinguish error/warning cases for bad jumps into constructs 

Previously, jumps to labels in constructs from exterior statements
would elicit only a warning.  Upgrade these to errors unless the
branch into the construct would enter into only DO, IF, and SELECT CASE
constructs, whose interiors don't scope variables or have other
set-up/tear-down semantics.  Branches into these "safe" constructs
are still errors if they're nested in an unsafe construct that doesn't
also enclose the exterior branch statement.

Differential Revision: https://reviews.llvm.org/D113310
This commit is contained in:
Peter Klausler 2021-10-29 16:23:22 -07:00
parent 1837a837b3
commit 80f0bb5971
3 changed files with 68 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

86
flang/lib/Semantics/resolve-labels.cpp
View File

@ -28,6 +28,12 @@ using IndexList = std::vector<std::pair<parser::CharBlock, parser::CharBlock>>;
// A ProxyForScope is an integral proxy for a Fortran scope. This is required
// because the parse tree does not actually have the scopes required.
using ProxyForScope = unsigned;
// Minimal scope information
struct ScopeInfo {
ProxyForScope parent{};
bool isExteriorGotoFatal{false};
int depth{0};
};
struct LabeledStatementInfoTuplePOD {
ProxyForScope proxyForScope;
parser::CharBlock parserCharBlock;
@ -153,14 +159,14 @@ static unsigned SayLabel(parser::Label label) {
}
struct UnitAnalysis {
UnitAnalysis() { scopeModel.push_back(0); }
UnitAnalysis() { scopeModel.emplace_back(); }
SourceStmtList doStmtSources;
SourceStmtList formatStmtSources;
SourceStmtList otherStmtSources;
SourceStmtList assignStmtSources;
TargetStmtMap targetStmts;
std::vector<ProxyForScope> scopeModel;
std::vector<ScopeInfo> scopeModel;
};
// Some parse tree record for statements simply wrap construct names;
@ -532,25 +538,34 @@ public:
SemanticsContext &ErrorHandler() { return context_; }
private:
bool PushSubscope() {
programUnits_.back().scopeModel.push_back(currentScope_);
currentScope_ = programUnits_.back().scopeModel.size() - 1;
return true;
ScopeInfo &PushScope() {
auto &model{programUnits_.back().scopeModel};
int newDepth{model.empty() ? 1 : model[currentScope_].depth + 1};
ScopeInfo &result{model.emplace_back()};
result.parent = currentScope_;
result.depth = newDepth;
currentScope_ = model.size() - 1;
return result;
}
bool InitializeNewScopeContext() {
programUnits_.emplace_back(UnitAnalysis{});
currentScope_ = 0u;
return PushSubscope();
PushScope();
return true;
}
void PopScope() {
currentScope_ = programUnits_.back().scopeModel[currentScope_];
ScopeInfo &PopScope() {
ScopeInfo &result{programUnits_.back().scopeModel[currentScope_]};
currentScope_ = result.parent;
return result;
}
ProxyForScope ParentScope() {
return programUnits_.back().scopeModel[currentScope_];
return programUnits_.back().scopeModel[currentScope_].parent;
}
bool SwitchToNewScope() {
PopScope();
return PushSubscope();
ScopeInfo &oldScope{PopScope()};
bool isExteriorGotoFatal{oldScope.isExteriorGotoFatal};
PushScope().isExteriorGotoFatal = isExteriorGotoFatal;
return true;
}
template <typename A> bool PushConstructName(const A &a) {
@ -558,7 +573,13 @@ private:
if (optionalName) {
constructNames_.emplace_back(optionalName->ToString());
}
return PushSubscope();
// Gotos into this construct from outside it are diagnosed, and
// are fatal unless the construct is a DO, IF, or SELECT CASE.
PushScope().isExteriorGotoFatal =
!(std::is_same_v<A, parser::DoConstruct> ||
std::is_same_v<A, parser::IfConstruct> ||
std::is_same_v<A, parser::CaseConstruct>);
return true;
}
bool PushConstructName(const parser::BlockConstruct &blockConstruct) {
const auto &optionalName{
@ -567,7 +588,8 @@ private:
if (optionalName) {
constructNames_.emplace_back(optionalName->ToString());
}
return PushSubscope();
PushScope().isExteriorGotoFatal = true;
return true;
}
template <typename A> void PopConstructNameIfPresent(const A &a) {
const auto &optionalName{std::get<0>(std::get<0>(a.t).statement.t)};
@ -796,9 +818,9 @@ private:
std::vector<std::string> constructNames_;
};
bool InInclusiveScope(const std::vector<ProxyForScope> &scopes,
ProxyForScope tail, ProxyForScope head) {
for (; tail != head; tail = scopes[tail]) {
bool InInclusiveScope(const std::vector<ScopeInfo> &scopes, ProxyForScope tail,
ProxyForScope head) {
for (; tail != head; tail = scopes[tail].parent) {
if (!HasScope(tail)) {
return false;
}
@ -881,13 +903,13 @@ parser::CharBlock SkipLabel(const parser::CharBlock &position) {
}
ProxyForScope ParentScope(
const std::vector<ProxyForScope> &scopes, ProxyForScope scope) {
return scopes[scope];
const std::vector<ScopeInfo> &scopes, ProxyForScope scope) {
return scopes[scope].parent;
}
void CheckLabelDoConstraints(const SourceStmtList &dos,
const SourceStmtList &branches, const TargetStmtMap &labels,
const std::vector<ProxyForScope> &scopes, SemanticsContext &context) {
const std::vector<ScopeInfo> &scopes, SemanticsContext &context) {
IndexList loopBodies;
for (const auto &stmt : dos) {
const auto &label{stmt.parserLabel};
@ -936,7 +958,7 @@ void CheckLabelDoConstraints(const SourceStmtList &dos,
// 6.2.5
void CheckScopeConstraints(const SourceStmtList &stmts,
const TargetStmtMap &labels, const std::vector<ProxyForScope> &scopes,
const TargetStmtMap &labels, const std::vector<ScopeInfo> &scopes,
SemanticsContext &context) {
for (const auto &stmt : stmts) {
const auto &label{stmt.parserLabel};
@ -955,8 +977,22 @@ void CheckScopeConstraints(const SourceStmtList &stmts,
TargetStatementEnum::Format)) {
continue;
}
bool isFatal{false};
ProxyForScope fromScope{scope};
for (ProxyForScope toScope{target.proxyForScope}; fromScope != toScope;
toScope = scopes[toScope].parent) {
if (scopes[toScope].isExteriorGotoFatal) {
isFatal = true;
break;
}
if (scopes[toScope].depth == scopes[fromScope].depth) {
fromScope = scopes[fromScope].parent;
}
}
context.Say(position,
"Label '%u' is in a construct that prevents its use as a branch target here"_en_US,
isFatal
? "Label '%u' is in a construct that prevents its use as a branch target here"_err_en_US
: "Label '%u' is in a construct that prevents its use as a branch target here"_en_US,
SayLabel(label));
}
}
@ -990,7 +1026,7 @@ void CheckBranchTargetConstraints(const SourceStmtList &stmts,
}
void CheckBranchConstraints(const SourceStmtList &branches,
const TargetStmtMap &labels, const std::vector<ProxyForScope> &scopes,
const TargetStmtMap &labels, const std::vector<ScopeInfo> &scopes,
SemanticsContext &context) {
CheckScopeConstraints(branches, labels, scopes, context);
CheckBranchTargetConstraints(branches, labels, context);
@ -1015,7 +1051,7 @@ void CheckDataXferTargetConstraints(const SourceStmtList &stmts,
}
void CheckDataTransferConstraints(const SourceStmtList &dataTransfers,
const TargetStmtMap &labels, const std::vector<ProxyForScope> &scopes,
const TargetStmtMap &labels, const std::vector<ScopeInfo> &scopes,
SemanticsContext &context) {
CheckScopeConstraints(dataTransfers, labels, scopes, context);
CheckDataXferTargetConstraints(dataTransfers, labels, context);
@ -1045,7 +1081,7 @@ void CheckAssignTargetConstraints(const SourceStmtList &stmts,
}
void CheckAssignConstraints(const SourceStmtList &assigns,
const TargetStmtMap &labels, const std::vector<ProxyForScope> &scopes,
const TargetStmtMap &labels, const std::vector<ScopeInfo> &scopes,
SemanticsContext &context) {
CheckScopeConstraints(assigns, labels, scopes, context);
CheckAssignTargetConstraints(assigns, labels, context);

9
flang/test/Semantics/label05.f90
View File

@ -1,12 +1,13 @@
! RUN: not %flang_fc1 -fdebug-unparse-with-symbols %s 2>&1 | FileCheck %s
! CHECK: Label '50' was not found
! CHECK-NOT: error: Label '55' is in a construct that prevents its use as a branch target here
! CHECK: Label '55' is in a construct that prevents its use as a branch target here
! CHECK: Label '70' is not a branch target
! CHECK: Control flow use of '70'
! CHECK: Label '80' is in a construct that prevents its use as a branch target here
! CHECK: Label '90' is in a construct that prevents its use as a branch target here
! CHECK: Label '91' is in a construct that prevents its use as a branch target here
! CHECK: Label '92' is in a construct that prevents its use as a branch target here
! CHECK: error: Label '80' is in a construct that prevents its use as a branch target here
! CHECK: error: Label '90' is in a construct that prevents its use as a branch target here
! CHECK: error: Label '91' is in a construct that prevents its use as a branch target here
! CHECK: error: Label '92' is in a construct that prevents its use as a branch target here
subroutine sub00(a,b,n,m)
real a(n,m)

4
flang/test/Semantics/label14.f90
View File

@ -1,8 +1,8 @@
! Tests implemented for this standard
! 11.1.4 - 4 It is permissible to branch to and end-block-stmt only withinh its
! 11.1.4 - 4 It is permissible to branch to an end-block-stmt only within its
! Block Construct
! RUN: %flang_fc1 -fsyntax-only %s 2>&1 | FileCheck %s
! RUN: not %flang_fc1 -fsyntax-only %s 2>&1 | FileCheck %s
! CHECK: Label '20' is in a construct that prevents its use as a branch target here
subroutine s1