Mordante created this revision.
Mordante added reviewers: aaron.ballman, rjmccall, rsmith.
Mordante added a project: clang.
Mordante requested review of this revision.
Adds a diagnostic when the user annotates an `if constexpr` with a likelihood
attribute. The `if constexpr` statement is evaluated at compile time so the
attribute has no effect. Annotating the accompanied `else` with a likelihood
attribute has the same effect as annotating a generic statement. Since the
attribute there is most likely not intended, a diagnostic will be issued. Since
the attributes can't conflict, the "conflict" won't be diagnosed for an `if
constexpr`.
It extends diagnostics on a patch in review.
Depends on D89899 <https://reviews.llvm.org/D89899>
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D90336
Files:
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaStmt.cpp
clang/test/SemaCXX/attr-likelihood.cpp
Index: clang/test/SemaCXX/attr-likelihood.cpp
===================================================================
--- clang/test/SemaCXX/attr-likelihood.cpp
+++ clang/test/SemaCXX/attr-likelihood.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -fsyntax-only -verify
+// RUN: %clang_cc1 %s -std=c++17 -fsyntax-only -verify
// RUN: %clang_cc1 %s -DPEDANTIC -pedantic -fsyntax-only -verify
#if PEDANTIC
@@ -129,4 +129,23 @@
catch (...) [[likely]] { // expected-error {{expected expression}}
}
}
+
+void o()
+{
+ // expected-warning@+2 {{attribute 'likely' has no effect when annotating an
'if constexpr' statement}}
+ // expected-note@+1 {{annotating the 'if constexpr' statement here}}
+ if constexpr (true) [[likely]];
+
+ // expected-note@+1 {{annotating the 'if constexpr' statement here}}
+ if constexpr (true) {
+ // expected-warning@+1 {{attribute 'unlikely' has no effect when annotating
an 'if constexpr' statement}}
+ } else [[unlikely]];
+
+ // Annotating both branches with conflicting likelihoods generates no
diagnostic regarding the conflict.
+ // expected-warning@+2 {{attribute 'likely' has no effect when annotating an
'if constexpr' statement}}
+ // expected-note@+1 2 {{annotating the 'if constexpr' statement here}}
+ if constexpr (true) [[likely]] {
+ // expected-warning@+1 {{attribute 'likely' has no effect when annotating an
'if constexpr' statement}}
+ } else [[likely]];
+}
#endif
Index: clang/lib/Sema/SemaStmt.cpp
===================================================================
--- clang/lib/Sema/SemaStmt.cpp
+++ clang/lib/Sema/SemaStmt.cpp
@@ -597,16 +597,29 @@
DiagnoseEmptyStmtBody(CondExpr->getEndLoc(), thenStmt,
diag::warn_empty_if_body);
- std::tuple<bool, const Attr *, const Attr *> LHC =
- Stmt::determineLikelihoodConflict(thenStmt, elseStmt);
- if (std::get<0>(LHC)) {
- const Attr *ThenAttr = std::get<1>(LHC);
- const Attr *ElseAttr = std::get<2>(LHC);
- Diags.Report(ThenAttr->getLocation(),
- diag::warn_attributes_likelihood_ifstmt_conflict)
- << ThenAttr << ThenAttr->getRange();
- Diags.Report(ElseAttr->getLocation(), diag::note_conflicting_attribute)
- << ElseAttr << ElseAttr->getRange();
+ if (IsConstexpr) {
+ auto DiagnoseLikelihood = [&](const Stmt *S) {
+ if (const Attr *A = Stmt::getLikelihoodAttr(S)) {
+ Diags.Report(A->getLocation(), diag::warn_attribute_has_no_effect)
+ << A << 1 << A->getRange();
+ Diags.Report(IfLoc, diag::note_attribute_has_no_effect_here)
+ << 1 << SourceRange(IfLoc, LParenLoc.getLocWithOffset(-1));
+ }
+ };
+ DiagnoseLikelihood(thenStmt);
+ DiagnoseLikelihood(elseStmt);
+ } else {
+ std::tuple<bool, const Attr *, const Attr *> LHC =
+ Stmt::determineLikelihoodConflict(thenStmt, elseStmt);
+ if (std::get<0>(LHC)) {
+ const Attr *ThenAttr = std::get<1>(LHC);
+ const Attr *ElseAttr = std::get<2>(LHC);
+ Diags.Report(ThenAttr->getLocation(),
+ diag::warn_attributes_likelihood_ifstmt_conflict)
+ << ThenAttr << ThenAttr->getRange();
+ Diags.Report(ElseAttr->getLocation(), diag::note_conflicting_attribute)
+ << ElseAttr << ElseAttr->getRange();
+ }
}
return BuildIfStmt(IfLoc, IsConstexpr, LParenLoc, InitStmt, Cond, RParenLoc,
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3156,10 +3156,11 @@
"__declspec attribute %0 is not supported">,
InGroup<IgnoredAttributes>;
def warn_attribute_has_no_effect : Warning<
- "attribute %0 has no effect when annotating %select{an infinite loop}1">,
+ "attribute %0 has no effect when annotating %select{an infinite loop|"
+ "an 'if constexpr' statement}1">,
InGroup<IgnoredAttributes>;
def note_attribute_has_no_effect_here : Note<
- "annotating the %select{infinite loop}0 here">;
+ "annotating the %select{infinite loop|'if constexpr' statement}0 here">;
def err_decl_attribute_invalid_on_stmt : Error<
"%0 attribute cannot be applied to a statement">;
def err_stmt_attribute_invalid_on_decl : Error<
Index: clang/test/SemaCXX/attr-likelihood.cpp
===================================================================
--- clang/test/SemaCXX/attr-likelihood.cpp
+++ clang/test/SemaCXX/attr-likelihood.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -fsyntax-only -verify
+// RUN: %clang_cc1 %s -std=c++17 -fsyntax-only -verify
// RUN: %clang_cc1 %s -DPEDANTIC -pedantic -fsyntax-only -verify
#if PEDANTIC
@@ -129,4 +129,23 @@
catch (...) [[likely]] { // expected-error {{expected expression}}
}
}
+
+void o()
+{
+ // expected-warning@+2 {{attribute 'likely' has no effect when annotating an 'if constexpr' statement}}
+ // expected-note@+1 {{annotating the 'if constexpr' statement here}}
+ if constexpr (true) [[likely]];
+
+ // expected-note@+1 {{annotating the 'if constexpr' statement here}}
+ if constexpr (true) {
+ // expected-warning@+1 {{attribute 'unlikely' has no effect when annotating an 'if constexpr' statement}}
+ } else [[unlikely]];
+
+ // Annotating both branches with conflicting likelihoods generates no diagnostic regarding the conflict.
+ // expected-warning@+2 {{attribute 'likely' has no effect when annotating an 'if constexpr' statement}}
+ // expected-note@+1 2 {{annotating the 'if constexpr' statement here}}
+ if constexpr (true) [[likely]] {
+ // expected-warning@+1 {{attribute 'likely' has no effect when annotating an 'if constexpr' statement}}
+ } else [[likely]];
+}
#endif
Index: clang/lib/Sema/SemaStmt.cpp
===================================================================
--- clang/lib/Sema/SemaStmt.cpp
+++ clang/lib/Sema/SemaStmt.cpp
@@ -597,16 +597,29 @@
DiagnoseEmptyStmtBody(CondExpr->getEndLoc(), thenStmt,
diag::warn_empty_if_body);
- std::tuple<bool, const Attr *, const Attr *> LHC =
- Stmt::determineLikelihoodConflict(thenStmt, elseStmt);
- if (std::get<0>(LHC)) {
- const Attr *ThenAttr = std::get<1>(LHC);
- const Attr *ElseAttr = std::get<2>(LHC);
- Diags.Report(ThenAttr->getLocation(),
- diag::warn_attributes_likelihood_ifstmt_conflict)
- << ThenAttr << ThenAttr->getRange();
- Diags.Report(ElseAttr->getLocation(), diag::note_conflicting_attribute)
- << ElseAttr << ElseAttr->getRange();
+ if (IsConstexpr) {
+ auto DiagnoseLikelihood = [&](const Stmt *S) {
+ if (const Attr *A = Stmt::getLikelihoodAttr(S)) {
+ Diags.Report(A->getLocation(), diag::warn_attribute_has_no_effect)
+ << A << 1 << A->getRange();
+ Diags.Report(IfLoc, diag::note_attribute_has_no_effect_here)
+ << 1 << SourceRange(IfLoc, LParenLoc.getLocWithOffset(-1));
+ }
+ };
+ DiagnoseLikelihood(thenStmt);
+ DiagnoseLikelihood(elseStmt);
+ } else {
+ std::tuple<bool, const Attr *, const Attr *> LHC =
+ Stmt::determineLikelihoodConflict(thenStmt, elseStmt);
+ if (std::get<0>(LHC)) {
+ const Attr *ThenAttr = std::get<1>(LHC);
+ const Attr *ElseAttr = std::get<2>(LHC);
+ Diags.Report(ThenAttr->getLocation(),
+ diag::warn_attributes_likelihood_ifstmt_conflict)
+ << ThenAttr << ThenAttr->getRange();
+ Diags.Report(ElseAttr->getLocation(), diag::note_conflicting_attribute)
+ << ElseAttr << ElseAttr->getRange();
+ }
}
return BuildIfStmt(IfLoc, IsConstexpr, LParenLoc, InitStmt, Cond, RParenLoc,
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3156,10 +3156,11 @@
"__declspec attribute %0 is not supported">,
InGroup<IgnoredAttributes>;
def warn_attribute_has_no_effect : Warning<
- "attribute %0 has no effect when annotating %select{an infinite loop}1">,
+ "attribute %0 has no effect when annotating %select{an infinite loop|"
+ "an 'if constexpr' statement}1">,
InGroup<IgnoredAttributes>;
def note_attribute_has_no_effect_here : Note<
- "annotating the %select{infinite loop}0 here">;
+ "annotating the %select{infinite loop|'if constexpr' statement}0 here">;
def err_decl_attribute_invalid_on_stmt : Error<
"%0 attribute cannot be applied to a statement">;
def err_stmt_attribute_invalid_on_decl : Error<
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