Index: include/clang/AST/Expr.h
===================================================================
--- include/clang/AST/Expr.h
+++ include/clang/AST/Expr.h
@@ -604,6 +604,11 @@
   bool EvaluateAsInt(EvalResult &Result, const ASTContext &Ctx,
                      SideEffectsKind AllowSideEffects = SE_NoSideEffects) const;
 
+  /// EvaluateAsIntInConstantContext - The same as EvaluteAsInt except we assume
+  /// that we're in a constant context.
+  bool EvaluateAsIntInConstantContext(EvalResult &Result,
+                                      const ASTContext &Ctx) const;
+
   /// EvaluateAsFloat - Return true if this is a constant which we can fold and
   /// convert to a floating point value, using any crazy technique that we
   /// want to.
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -10830,6 +10830,13 @@
   return ::EvaluateAsInt(this, Result, Ctx, AllowSideEffects, Info);
 }
 
+bool Expr::EvaluateAsIntInConstantContext(EvalResult &Result,
+                                          const ASTContext &Ctx) const {
+  EvalInfo Info(Ctx, Result, EvalInfo::EM_IgnoreSideEffects);
+  Info.InConstantContext = true;
+  return ::EvaluateAsInt(this, Result, Ctx, SE_NoSideEffects, Info);
+}
+
 bool Expr::EvaluateAsFloat(APFloat &Result, const ASTContext &Ctx,
                            SideEffectsKind AllowSideEffects) const {
   if (!getType()->isRealFloatingType())
Index: lib/CodeGen/CGStmt.cpp
===================================================================
--- lib/CodeGen/CGStmt.cpp
+++ lib/CodeGen/CGStmt.cpp
@@ -1821,7 +1821,12 @@
   // (immediate or symbolic), try to emit it as such.
   if (!Info.allowsRegister() && !Info.allowsMemory()) {
     Expr::EvalResult Result;
-    if (InputExpr->EvaluateAsInt(Result, getContext()))
+    bool Success = false;
+    if (CGM.getCodeGenOpts().OptimizationLevel > 0)
+      Success = InputExpr->EvaluateAsInt(Result, getContext());
+    else
+      Success = InputExpr->EvaluateAsIntInConstantContext(Result, getContext());
+    if (Success)
       return llvm::ConstantInt::get(getLLVMContext(), Result.Val.getInt());
     assert(!Info.requiresImmediateConstant() &&
            "Required-immediate inlineasm arg isn't constant?");
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 -O2 | FileCheck --check-prefix=O2 %s
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s -O0 | FileCheck --check-prefix=O0 %s
 
 int a = 42;
 
@@ -14,8 +15,8 @@
 struct foo f = (struct foo){ __builtin_constant_p(y), 42 };
 
 struct foo test0(int expr) {
-  // CHECK: define i64 @test0(i32 %expr)
-  // CHECK: call i1 @llvm.is.constant.i32(i32 %expr)
+  // O2: define i64 @test0(i32 %expr)
+  // O2: call i1 @llvm.is.constant.i32(i32 %expr)
   struct foo f = (struct foo){ __builtin_constant_p(expr), 42 };
   return f;
 }
@@ -27,15 +28,15 @@
 }
 
 int test1() {
-  // CHECK: define i32 @test1
-  // CHECK: add nsw i32 %0, -13
-  // CHECK-NEXT: call i1 @llvm.is.constant.i32(i32 %sub)
+  // O2: define i32 @test1
+  // O2: add nsw i32 %0, -13
+  // O2-NEXT: call i1 @llvm.is.constant.i32(i32 %sub)
   return bcp(test1_i(&a) - 13);
 }
 
 int test2() {
-  // CHECK: define i32 @test2
-  // CHECK: ret i32 0
+  // O2: define i32 @test2
+  // O2: ret i32 0
   return __builtin_constant_p(&a - 13);
 }
 
@@ -44,8 +45,8 @@
 }
 
 int test3() {
-  // CHECK: define i32 @test3
-  // CHECK: ret i32 1
+  // O2: define i32 @test3
+  // O2: ret i32 1
   return bcp(test3_i(&a) - 13);
 }
 
@@ -54,16 +55,16 @@
 int b[] = {1, 2, 3};
 
 int test4() {
-  // CHECK: define i32 @test4
-  // CHECK: ret i32 0
+  // O2: define i32 @test4
+  // O2: ret i32 0
   return __builtin_constant_p(b);
 }
 
 const char test5_c[] = {1, 2, 3, 0};
 
 int test5() {
-  // CHECK: define i32 @test5
-  // CHECK: ret i32 0
+  // O2: define i32 @test5
+  // O2: ret i32 0
   return __builtin_constant_p(test5_c);
 }
 
@@ -72,16 +73,16 @@
 }
 
 int test6() {
-  // CHECK: define i32 @test6
-  // CHECK: ret i32 0
+  // O2: define i32 @test6
+  // O2: ret i32 0
   return __builtin_constant_p(test6_i(test5_c));
 }
 
 /* --- Non-constant global variables */
 
 int test7() {
-  // CHECK: define i32 @test7
-  // CHECK: call i1 @llvm.is.constant.i32(i32 %0)
+  // O2: define i32 @test7
+  // O2: call i1 @llvm.is.constant.i32(i32 %0)
   return bcp(a);
 }
 
@@ -90,8 +91,8 @@
 const int c = 42;
 
 int test8() {
-  // CHECK: define i32 @test8
-  // CHECK: ret i32 1
+  // O2: define i32 @test8
+  // O2: ret i32 1
   return bcp(c);
 }
 
@@ -101,34 +102,34 @@
 const int c_arr[] = { 1, 2, 3 };
 
 int test9() {
-  // CHECK: define i32 @test9
-  // CHECK: call i1 @llvm.is.constant.i32(i32 %0)
+  // O2: define i32 @test9
+  // O2: call i1 @llvm.is.constant.i32(i32 %0)
   return __builtin_constant_p(arr[2]);
 }
 
 int test10() {
-  // CHECK: define i32 @test10
-  // CHECK: ret i32 1
+  // O2: define i32 @test10
+  // O2: ret i32 1
   return __builtin_constant_p(c_arr[2]);
 }
 
 int test11() {
-  // CHECK: define i32 @test11
-  // CHECK: ret i32 0
+  // O2: define i32 @test11
+  // O2: ret i32 0
   return __builtin_constant_p(c_arr);
 }
 
 /* --- Function pointers */
 
 int test12() {
-  // CHECK: define i32 @test12
-  // CHECK: ret i32 0
+  // O2: define i32 @test12
+  // O2: ret i32 0
   return __builtin_constant_p(&test10);
 }
 
 int test13() {
-  // CHECK: define i32 @test13
-  // CHECK: ret i32 1
+  // O2: define i32 @test13
+  // O2: ret i32 1
   return __builtin_constant_p(&test10 != 0);
 }
 
@@ -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) 
+  // O0: call void asm sideeffect "", {{.*}}(i32 -1) 
+  __asm__ __volatile__("" :: "n"( (__builtin_constant_p(test17_v) || 0) ? 1 : -1));
+  __asm__ __volatile__("" :: "i"( (__builtin_constant_p(test17_v) || 0) ? 1 : -1));
+}