Index: lib/Basic/TargetInfo.cpp
===================================================================
--- lib/Basic/TargetInfo.cpp
+++ lib/Basic/TargetInfo.cpp
@@ -685,7 +685,9 @@
       // FIXME: Fail if % is used with the last operand.
       break;
     case 'i': // immediate integer.
+      break;
     case 'n': // immediate integer with a known value.
+      Info.setRequiresImmediate();
       break;
     case 'I':  // Various constant constraints with target-specific meanings.
     case 'J':
Index: lib/CodeGen/CGStmt.cpp
===================================================================
--- lib/CodeGen/CGStmt.cpp
+++ lib/CodeGen/CGStmt.cpp
@@ -1820,11 +1820,14 @@
   // If this can't be a register or memory, i.e., has to be a constant
   // (immediate or symbolic), try to emit it as such.
   if (!Info.allowsRegister() && !Info.allowsMemory()) {
+    if (Info.requiresImmediateConstant()) {
+      llvm::APSInt AsmConst = InputExpr->EvaluateKnownConstInt(getContext());
+      return llvm::ConstantInt::get(getLLVMContext(), AsmConst);
+    }
+
     Expr::EvalResult Result;
     if (InputExpr->EvaluateAsInt(Result, getContext()))
       return llvm::ConstantInt::get(getLLVMContext(), Result.Val.getInt());
-    assert(!Info.requiresImmediateConstant() &&
-           "Required-immediate inlineasm arg isn't constant?");
   }
 
   if (Info.allowsRegister() || !Info.allowsMemory())
Index: lib/Sema/SemaStmtAsm.cpp
===================================================================
--- lib/Sema/SemaStmtAsm.cpp
+++ lib/Sema/SemaStmtAsm.cpp
@@ -378,17 +378,17 @@
                          << InputExpr->getSourceRange());
     } else if (Info.requiresImmediateConstant() && !Info.allowsRegister()) {
       if (!InputExpr->isValueDependent()) {
-        Expr::EvalResult EVResult;
-        if (!InputExpr->EvaluateAsInt(EVResult, Context))
+        llvm::SmallVector<PartialDiagnosticAt, 1> Diags;
+        llvm::APSInt Result = InputExpr->EvaluateKnownConstInt(Context, &Diags);
+        if (!Diags.empty())
           return StmtError(
               Diag(InputExpr->getBeginLoc(), diag::err_asm_immediate_expected)
               << Info.getConstraintStr() << InputExpr->getSourceRange());
-        llvm::APSInt Result = EVResult.Val.getInt();
-         if (!Info.isValidAsmImmediate(Result))
-           return StmtError(Diag(InputExpr->getBeginLoc(),
-                                 diag::err_invalid_asm_value_for_constraint)
-                            << Result.toString(10) << Info.getConstraintStr()
-                            << InputExpr->getSourceRange());
+        if (!Info.isValidAsmImmediate(Result))
+          return StmtError(Diag(InputExpr->getBeginLoc(),
+                                diag::err_invalid_asm_value_for_constraint)
+                           << Result.toString(10) << Info.getConstraintStr()
+                           << InputExpr->getSourceRange());
       }
 
     } else {
Index: test/CodeGen/builtin-constant-p.c
===================================================================
--- test/CodeGen/builtin-constant-p.c
+++ test/CodeGen/builtin-constant-p.c
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s -O2 | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s -O0 | FileCheck --check-prefix=O0 %s
 
 int a = 42;
 
@@ -166,3 +167,13 @@
 
 extern char test16_v;
 struct { int a; } test16 = { __builtin_constant_p(test16_v) };
+
+extern unsigned long long test17_v;
+
+void test17() {
+  // O0: define void @test17
+  // O0: call void asm sideeffect "", {{.*}}(i32 -1) 
+  // CHECK: define void @test17
+  // CHECK: call void asm sideeffect "", {{.*}}(i32 -1) 
+  __asm__ __volatile__("" :: "n"( (__builtin_constant_p(test17_v) || 0) ? 1 : -1));
+}