zequanwu updated this revision to Diff 261698.
zequanwu marked 4 inline comments as done.
zequanwu added a comment.
Add Sema test.
Check if nomerge attribute has no arguments and statement contains call
expressions.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D79121/new/
https://reviews.llvm.org/D79121
Files:
clang/include/clang/Basic/Attr.td
clang/include/clang/Basic/AttrDocs.td
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/CodeGen/CGCall.cpp
clang/lib/CodeGen/CGStmt.cpp
clang/lib/CodeGen/CodeGenFunction.h
clang/lib/Sema/SemaStmtAttr.cpp
clang/test/CodeGen/attr-nomerge.cpp
clang/test/Sema/attr-nomerge.cpp
Index: clang/test/Sema/attr-nomerge.cpp
===================================================================
--- /dev/null
+++ clang/test/Sema/attr-nomerge.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -verify -fsyntax-only %s
+
+void bar();
+
+void foo() {
+ [[clang::nomerge]] bar();
+ [[clang::nomerge(1, 2)]] bar(); // expected-error {{'nomerge' attribute takes no arguments}}
+ int x;
+ [[clang::nomerge]] x = 10; // expected-warning {{nomerge attribute is ignored because there exists no call expression inside the statement}}
+}
Index: clang/test/CodeGen/attr-nomerge.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGen/attr-nomerge.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -S -emit-llvm %s -o - | FileCheck %s
+
+bool bar();
+void f(bool, bool);
+
+void foo(int i) {
+ [[clang::nomerge]] bar();
+ [[clang::nomerge]] (i = 4, bar());
+ [[clang::nomerge]] (void)(bar());
+ [[clang::nomerge]] f(bar(), bar());
+ bar();
+}
+// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR:[0-9]+]]
+// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+// CHECK: call void @_Z1fbb({{.*}}) #[[NOMERGEATTR]]
+// CHECK-NEXT: call zeroext i1 @_Z3barv()
+// CHECK: attributes #[[NOMERGEATTR]] = { nomerge }
Index: clang/lib/Sema/SemaStmtAttr.cpp
===================================================================
--- clang/lib/Sema/SemaStmtAttr.cpp
+++ clang/lib/Sema/SemaStmtAttr.cpp
@@ -169,6 +169,28 @@
return LoopHintAttr::CreateImplicit(S.Context, Option, State, ValueExpr, A);
}
+static bool hasCallExpr(Stmt *S) {
+ if (S->getStmtClass() == Stmt::CallExprClass)
+ return true;
+ for (Stmt *SubStmt : S->children()) {
+ if (hasCallExpr(SubStmt))
+ return true;
+ }
+ return false;
+}
+
+static Attr *handleNoMergeAttr(Sema &S, Stmt *St, const ParsedAttr &A,
+ SourceRange Range) {
+ NoMergeAttr attribute(S.Context, A);
+ if (S.CheckAttrNoArgs(A))
+ return nullptr;
+ if (!hasCallExpr(St)) {
+ S.Diag(St->getBeginLoc(), diag::warn_nomerge_attribute_ignored_in_stmt)
+ << attribute.getSpelling();
+ return nullptr;
+ }
+ return ::new (S.Context) NoMergeAttr(S.Context, A);
+}
static void
CheckForIncompatibleAttributes(Sema &S,
@@ -335,6 +357,8 @@
return handleOpenCLUnrollHint(S, St, A, Range);
case ParsedAttr::AT_Suppress:
return handleSuppressAttr(S, St, A, Range);
+ case ParsedAttr::AT_NoMerge:
+ return handleNoMergeAttr(S, St, A, Range);
default:
// if we're here, then we parsed a known attribute, but didn't recognize
// it as a statement attribute => it is declaration attribute
Index: clang/lib/CodeGen/CodeGenFunction.h
===================================================================
--- clang/lib/CodeGen/CodeGenFunction.h
+++ clang/lib/CodeGen/CodeGenFunction.h
@@ -574,6 +574,9 @@
~SanitizerScope();
};
+ /// True if the current statement has nomerge attribute.
+ bool NoMerge = false;
+
/// In C++, whether we are code generating a thunk. This controls whether we
/// should emit cleanups.
bool CurFuncIsThunk = false;
Index: clang/lib/CodeGen/CGStmt.cpp
===================================================================
--- clang/lib/CodeGen/CGStmt.cpp
+++ clang/lib/CodeGen/CGStmt.cpp
@@ -608,7 +608,13 @@
}
void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
+ for (const auto *A: S.getAttrs())
+ if (A->getKind() == attr::NoMerge) {
+ NoMerge = true;
+ break;
+ }
EmitStmt(S.getSubStmt(), S.getAttrs());
+ NoMerge = false;
}
void CodeGenFunction::EmitGotoStmt(const GotoStmt &S) {
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -4523,6 +4523,12 @@
Attrs.addAttribute(getLLVMContext(), llvm::AttributeList::FunctionIndex,
llvm::Attribute::StrictFP);
+ // Add call-site nomerge attribute if exists.
+ if (NoMerge)
+ Attrs =
+ Attrs.addAttribute(getLLVMContext(), llvm::AttributeList::FunctionIndex,
+ llvm::Attribute::NoMerge);
+
// Apply some call-site-specific attributes.
// TODO: work this into building the attribute set.
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2751,6 +2751,9 @@
InGroup<DiagGroup<"auto-var-id">>;
// Attributes
+def warn_nomerge_attribute_ignored_in_stmt: Warning<
+ "%0 attribute is ignored because there exists no call expression inside the "
+ "statement">;
def err_nsobject_attribute : Error<
"'NSObject' attribute is for pointer types only">;
def err_attributes_are_not_compatible : Error<
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -350,6 +350,20 @@
}];
}
+def NoMergeDocs : Documentation {
+ let Category = DocCatFunction;
+ let Content = [{
+If a statement is marked ``nomerge`` and contains call experessions, those call
+expressions inside the statement will not be merged during optimization. This
+attribute can be used to prevent the optimizer from obscuring the source
+location of certain calls. For example, it will prevent tail merging otherwise
+identical code sequences that raise an exception or terminate the program. Tail
+merging normally reduces the precision of source location information, making
+stack traces less useful for debugging. This attribute gives the user control
+over the tradeoff between code size and debug information precision.
+ }];
+}
+
def AssertCapabilityDocs : Documentation {
let Category = DocCatFunction;
let Heading = "assert_capability, assert_shared_capability";
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1275,6 +1275,11 @@
let Documentation = [FallthroughDocs];
}
+def NoMerge : StmtAttr {
+ let Spellings = [Clang<"nomerge">];
+ let Documentation = [NoMergeDocs];
+}
+
def FastCall : DeclOrTypeAttr {
let Spellings = [GCC<"fastcall">, Keyword<"__fastcall">,
Keyword<"_fastcall">];
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