Implemented support for "pragma clang optimize on/off", based on attribute 'optnone'.

This patch implements support for selectively disabling optimizations on a
range of function definitions through a pragma. The implementation is that
all function definitions in the range are decorated with attribute
'optnone'.

    #pragma clang optimize off
    // All function definitions in here are decorated with 'optnone'.
    #pragma clang optimize on
    // Compilation resumes as normal.

llvm-svn: 209510

2 files changed, 33 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index bb25be7da17..6397487981b 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -470,6 +470,34 @@ void Sema::AddCFAuditedAttribute(Decl *D) {
   D->addAttr(CFAuditedTransferAttr::CreateImplicit(Context, Loc));
 }
 
+void Sema::ActOnPragmaOptimize(bool On, SourceLocation PragmaLoc) {
+  if(On)
+    OptimizeOffPragmaLocation = SourceLocation();
+  else
+    OptimizeOffPragmaLocation = PragmaLoc;
+}
+
+void Sema::AddRangeBasedOptnone(FunctionDecl *FD) {
+  // In the future, check other pragmas if they're implemented (e.g. pragma
+  // optimize 0 will probably map to this functionality too).
+  if(OptimizeOffPragmaLocation.isValid())
+    AddOptnoneAttributeIfNoConflicts(FD, OptimizeOffPragmaLocation);
+}
+
+void Sema::AddOptnoneAttributeIfNoConflicts(FunctionDecl *FD, 
+                                            SourceLocation Loc) {
+  // Don't add a conflicting attribute. No diagnostic is needed.
+  if (FD->hasAttr<MinSizeAttr>() || FD->hasAttr<AlwaysInlineAttr>())
+    return;
+
+  // Add attributes only if required. Optnone requires noinline as well, but if
+  // either is already present then don't bother adding them.
+  if (!FD->hasAttr<OptimizeNoneAttr>())
+    FD->addAttr(OptimizeNoneAttr::CreateImplicit(Context, Loc));
+  if (!FD->hasAttr<NoInlineAttr>())
+    FD->addAttr(NoInlineAttr::CreateImplicit(Context, Loc));
+}
+
 typedef std::vector<std::pair<unsigned, SourceLocation> > VisStack;
 enum : unsigned { NoVisibility = ~0U };
 
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index a3dd2e7462c..a522ef4784b 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7373,6 +7373,11 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
   // marking the function.
   AddCFAuditedAttribute(NewFD);
 
+  // If this is a function definition, check if we have to apply optnone due to
+  // a pragma.
+  if(D.isFunctionDefinition())
+    AddRangeBasedOptnone(NewFD);
+
   // If this is the first declaration of an extern C variable, update
   // the map of such variables.
   if (NewFD->isFirstDecl() && !NewFD->isInvalidDecl() &&