commit 899ded9cdf53b3d84c8d0e771851cc256296bfd2
author Hans Wennborg <hans@hanshq.net> Thu Oct 16 20:52:46 2014 +0000
committer Hans Wennborg <hans@hanshq.net> Thu Oct 16 20:52:46 2014 +0000
tree 05e0f0f099bab9d80d79172a08299e85c89d306f
parent 933bead97d1cd46e29d347329442a3c6f7259ce7

MS Compat: mark globals emitted in read-only sections const

They cannot be written to, so marking them const makes sense and may improve
optimisation.

As a side-effect, SectionInfos has to be moved from Sema to ASTContext.

It also fixes this problem, that occurs when compiling ATL:

  warning LNK4254: section 'ATL' (C0000040) merged into '.rdata' (40000040) with different attributes

The ATL headers are putting variables in a special section that's marked
read-only. However, Clang currently can't model that read-onlyness in the IR.
But, by making the variables const, the section does become read-only, and
the linker warning is avoided.

Differential Revision: http://reviews.llvm.org/D5812

llvm-svn: 219960

clang/lib/Sema/SemaAttr.cpp

diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index f92bb68..7629797 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -363,15 +363,15 @@
 bool Sema::UnifySection(StringRef SectionName,
                         int SectionFlags,
                         DeclaratorDecl *Decl) {
-  auto Section = SectionInfos.find(SectionName);
-  if (Section == SectionInfos.end()) {
-    SectionInfos[SectionName] =
-        SectionInfo(Decl, SourceLocation(), SectionFlags);
+  auto Section = Context.SectionInfos.find(SectionName);
+  if (Section == Context.SectionInfos.end()) {
+    Context.SectionInfos[SectionName] =
+        ASTContext::SectionInfo(Decl, SourceLocation(), SectionFlags);
     return false;
   }
   // A pre-declared section takes precedence w/o diagnostic.
   if (Section->second.SectionFlags == SectionFlags ||
-      !(Section->second.SectionFlags & PSF_Implicit))
+      !(Section->second.SectionFlags & ASTContext::PSF_Implicit))
     return false;
   auto OtherDecl = Section->second.Decl;
   Diag(Decl->getLocation(), diag::err_section_conflict)
@@ -390,11 +390,11 @@
 bool Sema::UnifySection(StringRef SectionName,
                         int SectionFlags,
                         SourceLocation PragmaSectionLocation) {
-  auto Section = SectionInfos.find(SectionName);
-  if (Section != SectionInfos.end()) {
+  auto Section = Context.SectionInfos.find(SectionName);
+  if (Section != Context.SectionInfos.end()) {
     if (Section->second.SectionFlags == SectionFlags)
       return false;
-    if (!(Section->second.SectionFlags & PSF_Implicit)) {
+    if (!(Section->second.SectionFlags & ASTContext::PSF_Implicit)) {
       Diag(PragmaSectionLocation, diag::err_section_conflict)
           << "this" << "a prior #pragma section";
       Diag(Section->second.PragmaSectionLocation,
@@ -402,8 +402,8 @@
       return true;
     }
   }
-  SectionInfos[SectionName] =
-      SectionInfo(nullptr, PragmaSectionLocation, SectionFlags);
+  Context.SectionInfos[SectionName] =
+      ASTContext::SectionInfo(nullptr, PragmaSectionLocation, SectionFlags);
   return false;
 }
 

clang/lib/Sema/SemaDecl.cpp

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 65eafd5..6f20c6a 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7334,7 +7334,9 @@
                                     CodeSegStack.CurrentValue->getString(),
                                     CodeSegStack.CurrentPragmaLocation));
     if (UnifySection(CodeSegStack.CurrentValue->getString(),
-                     PSF_Implicit | PSF_Execute | PSF_Read, NewFD))
+                     ASTContext::PSF_Implicit | ASTContext::PSF_Execute |
+                         ASTContext::PSF_Read,
+                     NewFD))
       NewFD->dropAttr<SectionAttr>();
   }
 
@@ -9403,15 +9405,15 @@
   if (var->isThisDeclarationADefinition() &&
       ActiveTemplateInstantiations.empty()) {
     PragmaStack<StringLiteral *> *Stack = nullptr;
-    int SectionFlags = PSF_Implicit | PSF_Read;
+    int SectionFlags = ASTContext::PSF_Implicit | ASTContext::PSF_Read;
     if (var->getType().isConstQualified())
       Stack = &ConstSegStack;
     else if (!var->getInit()) {
       Stack = &BSSSegStack;
-      SectionFlags |= PSF_Write;
+      SectionFlags |= ASTContext::PSF_Write;
     } else {
       Stack = &DataSegStack;
-      SectionFlags |= PSF_Write;
+      SectionFlags |= ASTContext::PSF_Write;
     }
     if (!var->hasAttr<SectionAttr>() && Stack->CurrentValue)
       var->addAttr(