ahatanak updated this revision to Diff 106735.
ahatanak marked 3 inline comments as done.
ahatanak added a comment.
Address review comments.
- Allow attaching "noescape" to pointers other than block pointers. Update the
docs accordingly.
- Attach attribute "nocapture" to parameters that are annotated with "noescape".
- Call Sema::isValidPointerAttrType to determine whether "noescape" can be
applied to a parameter. Also, use the existing warning
"warn_attribute_pointers_only" rather than defining a new warning that will be
used just for noescape.
I also thought about what else we can do in the front-end when a parameter has
'noescape". One idea is to do something similar to what r301667 did and omit
emitting retains and releases of block captures when the block is passed to a
function taking a noescape parameter. If that is viable, I can look into it
after committing this patch.
https://reviews.llvm.org/D32210
Files:
include/clang/AST/Type.h
include/clang/Basic/Attr.td
include/clang/Basic/AttrDocs.td
lib/CodeGen/CGCall.cpp
lib/Sema/SemaDeclAttr.cpp
lib/Sema/SemaType.cpp
test/CodeGenObjC/noescape.m
test/SemaObjCXX/noescape.mm
Index: test/SemaObjCXX/noescape.mm
===================================================================
--- /dev/null
+++ test/SemaObjCXX/noescape.mm
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -fblocks -std=c++11 %s
+
+typedef void (^BlockTy)();
+
+struct S {
+ int i;
+ void m();
+};
+
+void noescapeFunc0(id, __attribute__((noescape)) BlockTy);
+void noescapeFunc1(id, [[clang::noescape]] BlockTy);
+void noescapeFunc2(__attribute__((noescape)) int *);
+void noescapeFunc3(__attribute__((noescape)) id);
+void noescapeFunc4(__attribute__((noescape)) int &);
+
+void invalidFunc0(int __attribute__((noescape))); // expected-warning {{'noescape' attribute only applies to pointer arguments}}
+void invalidFunc1(int __attribute__((noescape(0)))); // expected-error {{'noescape' attribute takes no arguments}}
+void invalidFunc2(int0 *__attribute__((noescape))); // expected-error {{use of undeclared identifier 'int0'; did you mean 'int'?}}
+void invalidFunc3(__attribute__((noescape)) int (S::*Ty)); // expected-warning {{'noescape' attribute only applies to pointer arguments}}
+void invalidFunc4(__attribute__((noescape)) void (S::*Ty)()); // expected-warning {{'noescape' attribute only applies to pointer arguments}}
+int __attribute__((noescape)) g; // expected-warning {{'noescape' attribute only applies to parameters}}
Index: test/CodeGenObjC/noescape.m
===================================================================
--- /dev/null
+++ test/CodeGenObjC/noescape.m
@@ -0,0 +1,41 @@
+// RUN: %clang_cc1 -fblocks -emit-llvm -o - %s | FileCheck %s
+
+typedef void (^BlockTy)(void);
+
+union U {
+ int *i;
+ long long *ll;
+} __attribute__((transparent_union));
+
+void noescapeFunc0(id, __attribute__((noescape)) BlockTy);
+void noescapeFunc1(__attribute__((noescape)) int *);
+void noescapeFunc2(__attribute__((noescape)) id);
+void noescapeFunc3(__attribute__((noescape)) union U);
+
+// CHECK-LABEL: define void @test0(
+// CHECK: call void @noescapeFunc0({{.*}}, [[TY0:.*]] nocapture {{.*}})
+// CHECK: declare void @noescapeFunc0(i8*, [[TY0]] nocapture)
+void test0(BlockTy b) {
+ noescapeFunc0(0, b);
+}
+
+// CHECK-LABEL: define void @test1(
+// CHECK: call void @noescapeFunc1([[TY1:.*]] nocapture {{.*}})
+// CHECK: declare void @noescapeFunc1([[TY1]] nocapture)
+void test1(int *i) {
+ noescapeFunc1(i);
+}
+
+// CHECK-LABEL: define void @test2(
+// CHECK: call void @noescapeFunc2([[TY2:.*]] nocapture {{.*}})
+// CHECK: declare void @noescapeFunc2([[TY2]] nocapture)
+void test2(id i) {
+ noescapeFunc2(i);
+}
+
+// CHECK-LABEL: define void @test3(
+// CHECK: call void @noescapeFunc3([[TY3:.*]] nocapture {{.*}})
+// CHECK: declare void @noescapeFunc3([[TY3]] nocapture)
+void test3(union U u) {
+ noescapeFunc3(u);
+}
Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -4478,6 +4478,11 @@
HasAnyInterestingExtParameterInfos = true;
}
+ if (Param->hasAttr<NoEscapeAttr>()) {
+ ExtParameterInfos[i] = ExtParameterInfos[i].withIsNoEscape();
+ HasAnyInterestingExtParameterInfos = true;
+ }
+
ParamTys.push_back(ParamTy);
}
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -1517,6 +1517,22 @@
Attr.getAttributeSpellingListIndex()));
}
+static void handleNoEscapeAttr(Sema &S, Decl *D, const AttributeList &Attr) {
+ if (D->isInvalidDecl())
+ return;
+
+ // noescape only applies to pointer types.
+ QualType T = cast<ParmVarDecl>(D)->getType();
+ if (!S.isValidPointerAttrType(T, /* RefOkay */ true)) {
+ S.Diag(Attr.getLoc(), diag::warn_attribute_pointers_only)
+ << Attr.getName() << Attr.getRange() << 0;
+ return;
+ }
+
+ D->addAttr(::new (S.Context) NoEscapeAttr(
+ Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));
+}
+
static void handleAssumeAlignedAttr(Sema &S, Decl *D,
const AttributeList &Attr) {
Expr *E = Attr.getArgAsExpr(0),
@@ -6105,6 +6121,9 @@
case AttributeList::AT_ReturnsNonNull:
handleReturnsNonNullAttr(S, D, Attr);
break;
+ case AttributeList::AT_NoEscape:
+ handleNoEscapeAttr(S, D, Attr);
+ break;
case AttributeList::AT_AssumeAligned:
handleAssumeAlignedAttr(S, D, Attr);
break;
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -2092,6 +2092,9 @@
break;
}
+ if (FI.getExtParameterInfo(ArgNo).isNoEscape())
+ Attrs.addAttribute(llvm::Attribute::NoCapture);
+
if (Attrs.hasAttributes()) {
unsigned FirstIRArg, NumIRArgs;
std::tie(FirstIRArg, NumIRArgs) = IRFunctionArgs.getIRArgs(ArgNo);
Index: include/clang/Basic/AttrDocs.td
===================================================================
--- include/clang/Basic/AttrDocs.td
+++ include/clang/Basic/AttrDocs.td
@@ -112,6 +112,46 @@
}];
}
+def NoEscapeDocs : Documentation {
+ let Category = DocCatVariable;
+ let Content = [{
+``noescape`` placed on a function parameter of a pointer type is used to inform
+the compiler that the pointer cannot escape: that is, no reference to the object
+the pointer points to that is derived from the parameter value will survive
+after the function returns. Users are responsible for making sure parameters
+annotated with ``noescape`` do not actuallly escape.
+
+For example:
+
+.. code-block:: c
+ int *gp;
+
+ void nonescapingFunc(__attribute__((noescape)) int *p) {
+ *p += 100; // OK.
+ }
+
+ void escapingFunc(__attribute__((noescape)) int *p) {
+ gp = p; // Not OK.
+ }
+
+Additionally, for block pointers, the same restriction apply to copies of
+blocks. For example:
+
+ typedef void (^BlockTy)();
+ BlockTy g0, g1;
+
+ void nonescapingFunc(__attribute__((noescape)) BlockTy block) {
+ block(); // OK.
+ }
+
+ void escapingFunc(__attribute__((noescape)) BlockTy block) {
+ g0 = block; // Not OK.
+ g1 = Block_copy(block); // Not OK either.
+ }
+
+ }];
+}
+
def CarriesDependencyDocs : Documentation {
let Category = DocCatFunction;
let Content = [{
Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -1383,6 +1383,12 @@
let Documentation = [Undocumented];
}
+def NoEscape : InheritableParamAttr {
+ let Spellings = [GNU<"noescape">, CXX11<"clang", "noescape">];
+ let Subjects = SubjectList<[ParmVar]>;
+ let Documentation = [NoEscapeDocs];
+}
+
def AssumeAligned : InheritableAttr {
let Spellings = [GCC<"assume_aligned">];
let Subjects = SubjectList<[ObjCMethod, Function]>;
Index: include/clang/AST/Type.h
===================================================================
--- include/clang/AST/Type.h
+++ include/clang/AST/Type.h
@@ -3151,6 +3151,7 @@
ABIMask = 0x0F,
IsConsumed = 0x10,
HasPassObjSize = 0x20,
+ IsNoEscape = 0x40,
};
unsigned char Data;
@@ -3191,6 +3192,16 @@
return Copy;
}
+ bool isNoEscape() const {
+ return Data & IsNoEscape;
+ }
+
+ ExtParameterInfo withIsNoEscape() const {
+ ExtParameterInfo Copy = *this;
+ Copy.Data |= IsNoEscape;
+ return Copy;
+ }
+
unsigned char getOpaqueValue() const { return Data; }
static ExtParameterInfo getFromOpaqueValue(unsigned char data) {
ExtParameterInfo result;
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