Index: test/CodeGen/asm-const-type-qualifier.c
===================================================================
--- test/CodeGen/asm-const-type-qualifier.c	(revision 0)
+++ test/CodeGen/asm-const-type-qualifier.c	(revision 0)
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 -O3 -triple x86_64-apple-darwin10 -emit-llvm %s -o - | FileCheck %s
+
+void **foo(void) {
+    void *ptr;
+    asm const("mov $0x12345678, %0" : "=r" (ptr));
+    return ptr;
+}
+// Check for the constant type-qualifier and readnone attribute
+// CHECK: @foo
+// CHECK: entry:
+// CHECK: call i8* asm constant "mov $$0x12345678, $0", "=r,~{dirflag},~{fpsr},~{flags}"() nounwind readnone
+// CHECK: ret
+
+static inline void **varptr(void) {
+    void *ptr;
+    asm const("mov $0x12345678, %0" : "=r" (ptr));
+    return ptr;
+}
+static inline void *getvar(void) { return *varptr(); }
+static inline void setvar(void *value) { *varptr() = value; }
+void fn(void) { if (getvar()) setvar(0); }
+
+// Check to see if the second inline asm is CSE'ed after inlining
+// CHECK: @fn
+// CHECK: entry:
+// CHECK: call i8* asm constant "mov $$0x12345678, $0", "=r,~{dirflag},~{fpsr},~{flags}"() nounwind readnone
+// CHECK-NOT: call i8* asm constant "mov $$0x12345678, $0", "=r,~{dirflag},~{fpsr},~{flags}"() nounwind readnone
+// CHECK: ret
+
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h	(revision 156383)
+++ include/clang/Sema/Sema.h	(working copy)
@@ -2490,7 +2490,7 @@
   StmtResult ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp);
 
   StmtResult ActOnAsmStmt(SourceLocation AsmLoc,
-                          bool IsSimple, bool IsVolatile,
+                          bool IsSimple, bool IsVolatile, bool IsConst,
                           unsigned NumOutputs, unsigned NumInputs,
                           IdentifierInfo **Names,
                           MultiExprArg Constraints,
Index: include/clang/AST/Stmt.h
===================================================================
--- include/clang/AST/Stmt.h	(revision 156383)
+++ include/clang/AST/Stmt.h	(working copy)
@@ -1366,6 +1366,7 @@
 
   bool IsSimple;
   bool IsVolatile;
+  bool IsConst;
   bool MSAsm;
 
   unsigned NumOutputs;
@@ -1380,7 +1381,7 @@
 
 public:
   AsmStmt(ASTContext &C, SourceLocation asmloc, bool issimple, bool isvolatile,
-          bool msasm, unsigned numoutputs, unsigned numinputs,
+          bool isconst, bool msasm, unsigned numoutputs, unsigned numinputs,
           IdentifierInfo **names, StringLiteral **constraints,
           Expr **exprs, StringLiteral *asmstr, unsigned numclobbers,
           StringLiteral **clobbers, SourceLocation rparenloc);
@@ -1396,6 +1397,8 @@
 
   bool isVolatile() const { return IsVolatile; }
   void setVolatile(bool V) { IsVolatile = V; }
+  bool isConst() const { return IsConst; }
+  void setConst(bool C) { IsConst = C; }
   bool isSimple() const { return IsSimple; }
   void setSimple(bool V) { IsSimple = V; }
   bool isMSAsm() const { return MSAsm; }
Index: lib/Sema/TreeTransform.h
===================================================================
--- lib/Sema/TreeTransform.h	(revision 156383)
+++ lib/Sema/TreeTransform.h	(working copy)
@@ -1164,6 +1164,7 @@
   StmtResult RebuildAsmStmt(SourceLocation AsmLoc,
                                   bool IsSimple,
                                   bool IsVolatile,
+                                  bool IsConst,
                                   unsigned NumOutputs,
                                   unsigned NumInputs,
                                   IdentifierInfo **Names,
@@ -1173,9 +1174,9 @@
                                   MultiExprArg Clobbers,
                                   SourceLocation RParenLoc,
                                   bool MSAsm) {
-    return getSema().ActOnAsmStmt(AsmLoc, IsSimple, IsVolatile, NumOutputs, 
-                                  NumInputs, Names, move(Constraints),
-                                  Exprs, AsmString, Clobbers,
+    return getSema().ActOnAsmStmt(AsmLoc, IsSimple, IsVolatile, IsConst,
+                                  NumOutputs, NumInputs, Names, 
+                                  move(Constraints), Exprs, AsmString, Clobbers,
                                   RParenLoc, MSAsm);
   }
 
@@ -5591,6 +5592,7 @@
   return getDerived().RebuildAsmStmt(S->getAsmLoc(),
                                      S->isSimple(),
                                      S->isVolatile(),
+                                     S->isConst(),
                                      S->getNumOutputs(),
                                      S->getNumInputs(),
                                      Names.data(),
Index: lib/Sema/SemaStmt.cpp
===================================================================
--- lib/Sema/SemaStmt.cpp	(revision 156383)
+++ lib/Sema/SemaStmt.cpp	(working copy)
@@ -2420,7 +2420,7 @@
 }
 
 StmtResult Sema::ActOnAsmStmt(SourceLocation AsmLoc, bool IsSimple,
-                              bool IsVolatile, unsigned NumOutputs,
+                              bool IsVolatile, bool IsConst,unsigned NumOutputs,
                               unsigned NumInputs, IdentifierInfo **Names,
                               MultiExprArg constraints, MultiExprArg exprs,
                               Expr *asmString, MultiExprArg clobbers,
@@ -2529,7 +2529,7 @@
   }
 
   AsmStmt *NS =
-    new (Context) AsmStmt(Context, AsmLoc, IsSimple, IsVolatile, MSAsm,
+    new (Context) AsmStmt(Context, AsmLoc, IsSimple, IsVolatile, IsConst, MSAsm,
                           NumOutputs, NumInputs, Names, Constraints, Exprs,
                           AsmString, NumClobbers, Clobbers, RParenLoc);
   // Validate the asm string, ensuring it makes sense given the operands we
Index: lib/AST/Stmt.cpp
===================================================================
--- lib/AST/Stmt.cpp	(revision 156383)
+++ lib/AST/Stmt.cpp	(working copy)
@@ -526,13 +526,13 @@
 //===----------------------------------------------------------------------===//
 
 AsmStmt::AsmStmt(ASTContext &C, SourceLocation asmloc, bool issimple, 
-                 bool isvolatile, bool msasm, 
+                 bool isvolatile, bool isconst, bool msasm, 
                  unsigned numoutputs, unsigned numinputs,
                  IdentifierInfo **names, StringLiteral **constraints,
                  Expr **exprs, StringLiteral *asmstr, unsigned numclobbers,
                  StringLiteral **clobbers, SourceLocation rparenloc)
   : Stmt(AsmStmtClass), AsmLoc(asmloc), RParenLoc(rparenloc), AsmStr(asmstr)
-  , IsSimple(issimple), IsVolatile(isvolatile), MSAsm(msasm)
+  , IsSimple(issimple), IsVolatile(isvolatile), IsConst(isconst), MSAsm(msasm)
   , NumOutputs(numoutputs), NumInputs(numinputs), NumClobbers(numclobbers) {
 
   unsigned NumExprs = NumOutputs +NumInputs;
Index: lib/CodeGen/CGStmt.cpp
===================================================================
--- lib/CodeGen/CGStmt.cpp	(revision 156383)
+++ lib/CodeGen/CGStmt.cpp	(working copy)
@@ -1630,9 +1630,12 @@
 
   llvm::InlineAsm *IA =
     llvm::InlineAsm::get(FTy, AsmString, Constraints,
-                         S.isVolatile() || S.getNumOutputs() == 0);
+                         S.isVolatile() || S.getNumOutputs() == 0, 
+                         /* isAlignStack */false, S.isConst());
   llvm::CallInst *Result = Builder.CreateCall(IA, Args);
   Result->addAttribute(~0, llvm::Attribute::NoUnwind);
+  if (S.isConst())
+    Result->addAttribute(~0, llvm::Attribute::ReadNone);
 
   // Slap the source location of the inline asm into a !srcloc metadata on the
   // call.
Index: lib/Parse/ParseStmt.cpp
===================================================================
--- lib/Parse/ParseStmt.cpp	(revision 156383)
+++ lib/Parse/ParseStmt.cpp	(working copy)
@@ -1733,7 +1733,7 @@
   ExprVector Constraints(Actions);
   ExprVector Exprs(Actions);
   ExprVector Clobbers(Actions);
-  return Actions.ActOnAsmStmt(AsmLoc, true, true, 0, 0, 0,
+  return Actions.ActOnAsmStmt(AsmLoc, true, true, false, 0, 0, 0,
                               move_arg(Constraints), move_arg(Exprs),
                               AsmString.take(), move_arg(Clobbers),
                               EndLoc, true);
@@ -1783,12 +1783,12 @@
   ParseTypeQualifierListOpt(DS, true, false);
 
   // GNU asms accept, but warn, about type-qualifiers other than volatile.
-  if (DS.getTypeQualifiers() & DeclSpec::TQ_const)
-    Diag(Loc, diag::w_asm_qualifier_ignored) << "const";
+  // However, clang does support the const type-qualifier.
   if (DS.getTypeQualifiers() & DeclSpec::TQ_restrict)
     Diag(Loc, diag::w_asm_qualifier_ignored) << "restrict";
 
-  // Remember if this was a volatile asm.
+  // Remember if this was a const/volatile asm.
+  bool isConst = DS.getTypeQualifiers() & DeclSpec::TQ_const;
   bool isVolatile = DS.getTypeQualifiers() & DeclSpec::TQ_volatile;
   if (Tok.isNot(tok::l_paren)) {
     Diag(Tok, diag::err_expected_lparen_after) << "asm";
@@ -1813,7 +1813,7 @@
   if (Tok.is(tok::r_paren)) {
     // We have a simple asm expression like 'asm("foo")'.
     T.consumeClose();
-    return Actions.ActOnAsmStmt(AsmLoc, /*isSimple*/ true, isVolatile,
+    return Actions.ActOnAsmStmt(AsmLoc, /*isSimple*/ true, isVolatile, isConst,
                                 /*NumOutputs*/ 0, /*NumInputs*/ 0, 0,
                                 move_arg(Constraints), move_arg(Exprs),
                                 AsmString.take(), move_arg(Clobbers),
@@ -1878,7 +1878,7 @@
   }
 
   T.consumeClose();
-  return Actions.ActOnAsmStmt(AsmLoc, false, isVolatile,
+  return Actions.ActOnAsmStmt(AsmLoc, false, isVolatile, isConst,
                               NumOutputs, NumInputs, Names.data(),
                               move_arg(Constraints), move_arg(Exprs),
                               AsmString.take(), move_arg(Clobbers),