Non-allocatable Global Named Register

This patch implements global named registers in Clang, lowering to the just
created intrinsics in LLVM (@llvm.read/write_register). A new type of LValue
had to be created (Register), which just adds support to carry the metadata
node containing the name of the register. Two new methods to emit loads and
stores interoperate with another to emit the named metadata node.

No guarantees are being made and only non-allocatable global variable named
registers are being supported. Local named register support is unchanged.

llvm-svn: 209149

1 files changed, 8 insertions, 7 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 3c19e9632f6..5276cafcf72 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5119,13 +5119,9 @@ Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
   if (!DC->isRecord() && S->getFnParent() == 0) {
     // C99 6.9p2: The storage-class specifiers auto and register shall not
     // appear in the declaration specifiers in an external declaration.
-    if (SC == SC_Auto || SC == SC_Register) {
-      // If this is a register variable with an asm label specified, then this
-      // is a GNU extension.
-      if (SC == SC_Register && D.getAsmLabel())
-        Diag(D.getIdentifierLoc(), diag::err_unsupported_global_register);
-      else
-        Diag(D.getIdentifierLoc(), diag::err_typecheck_sclass_fscope);
+    // Global Register+Asm is a GNU extension we support.
+    if (SC == SC_Auto || (SC == SC_Register && !D.getAsmLabel())) {
+      Diag(D.getIdentifierLoc(), diag::err_typecheck_sclass_fscope);
       D.setInvalidType();
     }
   }
@@ -5437,6 +5433,7 @@ Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
         Diag(E->getExprLoc(), diag::warn_asm_label_on_auto_decl) << Label;
         break;
       case SC_Register:
+        // Local Named register
         if (!Context.getTargetInfo().isValidGCCRegisterName(Label))
           Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
         break;
@@ -5446,6 +5443,10 @@ Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
       case SC_OpenCLWorkGroupLocal:
         break;
       }
+    } else if (SC == SC_Register) {
+      // Global Named register
+      if (!Context.getTargetInfo().isValidGCCRegisterName(Label))
+        Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
     }
 
     NewVD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0),