Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -1994,9 +1994,14 @@
     if (TargetDecl->hasAttr<ConstAttr>()) {
       FuncAttrs.addAttribute(llvm::Attribute::ReadNone);
       FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
+      // gcc specifies that 'const' functions have greater restrictions than
+      // 'pure' functions, so they also cannot have infinite loops.
+      FuncAttrs.addAttribute(llvm::Attribute::WillReturn);
     } else if (TargetDecl->hasAttr<PureAttr>()) {
       FuncAttrs.addAttribute(llvm::Attribute::ReadOnly);
       FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
+      // gcc specifies that 'pure' functions cannot have infinite loops.
+      FuncAttrs.addAttribute(llvm::Attribute::WillReturn);
     } else if (TargetDecl->hasAttr<NoAliasAttr>()) {
       FuncAttrs.addAttribute(llvm::Attribute::ArgMemOnly);
       FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
Index: clang/test/CodeGen/complex-builtins.c
===================================================================
--- clang/test/CodeGen/complex-builtins.c
+++ clang/test/CodeGen/complex-builtins.c
@@ -133,7 +133,7 @@
 // NO__ERRNO: declare { x86_fp80, x86_fp80 } @cprojl({ x86_fp80, x86_fp80 }* byval({ x86_fp80, x86_fp80 }) align 16) [[NOT_READNONE]]
 // HAS_ERRNO: declare { double, double } @cproj(double, double) [[READNONE:#[0-9]+]]
 // HAS_ERRNO: declare <2 x float> @cprojf(<2 x float>) [[READNONE]]
-// HAS_ERRNO: declare { x86_fp80, x86_fp80 } @cprojl({ x86_fp80, x86_fp80 }* byval({ x86_fp80, x86_fp80 }) align 16) [[NOT_READNONE]]
+// HAS_ERRNO: declare { x86_fp80, x86_fp80 } @cprojl({ x86_fp80, x86_fp80 }* byval({ x86_fp80, x86_fp80 }) align 16) [[WILLRETURN_NOT_READNONE:#[0-9]+]]
 
   __builtin_cpow(f,f);       __builtin_cpowf(f,f);      __builtin_cpowl(f,f);
 
@@ -202,3 +202,4 @@
 
 // HAS_ERRNO: attributes [[NOT_READNONE]] = { nounwind {{.*}} }
 // HAS_ERRNO: attributes [[READNONE]] = { {{.*}}readnone{{.*}} }
+// HAS_ERRNO: attributes [[WILLRETURN_NOT_READNONE]] = { nounwind willreturn {{.*}} }
Index: clang/test/CodeGen/complex-libcalls.c
===================================================================
--- clang/test/CodeGen/complex-libcalls.c
+++ clang/test/CodeGen/complex-libcalls.c
@@ -133,7 +133,7 @@
 // NO__ERRNO: declare { x86_fp80, x86_fp80 } @cprojl({ x86_fp80, x86_fp80 }* byval({ x86_fp80, x86_fp80 }) align 16) [[NOT_READNONE]]
 // HAS_ERRNO: declare { double, double } @cproj(double, double) [[READNONE:#[0-9]+]]
 // HAS_ERRNO: declare <2 x float> @cprojf(<2 x float>) [[READNONE]]
-// HAS_ERRNO: declare { x86_fp80, x86_fp80 } @cprojl({ x86_fp80, x86_fp80 }* byval({ x86_fp80, x86_fp80 }) align 16) [[NOT_READNONE]]
+// HAS_ERRNO: declare { x86_fp80, x86_fp80 } @cprojl({ x86_fp80, x86_fp80 }* byval({ x86_fp80, x86_fp80 }) align 16) [[WILLRETURN_NOT_READNONE:#[0-9]+]]
 
   cpow(f,f);       cpowf(f,f);      cpowl(f,f);
 
@@ -202,3 +202,4 @@
 
 // HAS_ERRNO: attributes [[NOT_READNONE]] = { nounwind {{.*}} }
 // HAS_ERRNO: attributes [[READNONE]] = { {{.*}}readnone{{.*}} }
+// HAS_ERRNO: attributes [[WILLRETURN_NOT_READNONE]] = { nounwind willreturn {{.*}} }
Index: clang/test/CodeGen/function-attributes.c
===================================================================
--- clang/test/CodeGen/function-attributes.c
+++ clang/test/CodeGen/function-attributes.c
@@ -115,5 +115,5 @@
 // CHECK: attributes [[SR]] = { nounwind optsize{{.*}} "stackrealign"{{.*}} }
 // CHECK: attributes [[RT]] = { nounwind optsize returns_twice{{.*}} }
 // CHECK: attributes [[NR]] = { noreturn optsize }
-// CHECK: attributes [[NUW_RN]] = { nounwind optsize readnone }
+// CHECK: attributes [[NUW_RN]] = { nounwind optsize readnone willreturn }
 // CHECK: attributes [[RT_CALL]] = { optsize returns_twice }
Index: clang/test/CodeGenCXX/2009-05-04-PureConstNounwind.cpp
===================================================================
--- clang/test/CodeGenCXX/2009-05-04-PureConstNounwind.cpp
+++ clang/test/CodeGenCXX/2009-05-04-PureConstNounwind.cpp
@@ -15,8 +15,8 @@
 // CHECK: declare i32 @_Z1tv() [[TF2:#[0-9]+]]
 
 // CHECK: attributes [[TF]] = { {{.*}} }
-// CHECK: attributes [[NUW_RN]] = { nounwind readnone{{.*}} }
-// CHECK: attributes [[NUW_RO]] = { nounwind readonly{{.*}} }
+// CHECK: attributes [[NUW_RN]] = { nounwind readnone willreturn{{.*}} }
+// CHECK: attributes [[NUW_RO]] = { nounwind readonly willreturn{{.*}} }
 // CHECK: attributes [[TF2]] = { {{.*}} }
-// CHECK: attributes [[NUW_RN_CALL]] = { nounwind readnone }
-// CHECK: attributes [[NUW_RO_CALL]] = { nounwind readonly }
+// CHECK: attributes [[NUW_RN_CALL]] = { nounwind readnone willreturn }
+// CHECK: attributes [[NUW_RO_CALL]] = { nounwind readonly willreturn }
Index: clang/test/Sema/libbuiltins-ctype-powerpc64.c
===================================================================
--- clang/test/Sema/libbuiltins-ctype-powerpc64.c
+++ clang/test/Sema/libbuiltins-ctype-powerpc64.c
@@ -62,4 +62,4 @@
 // CHECK: declare signext i32 @toupper(i32 signext) [[NUW_RO:#[0-9]+]]
 
 // CHECK: attributes [[NUW_RO]] = { nounwind readonly{{.*}} }
-// CHECK: attributes [[NUW_RO_CALL]] = { nounwind readonly }
+// CHECK: attributes [[NUW_RO_CALL]] = { nounwind readonly willreturn }
Index: clang/test/Sema/libbuiltins-ctype-x86_64.c
===================================================================
--- clang/test/Sema/libbuiltins-ctype-x86_64.c
+++ clang/test/Sema/libbuiltins-ctype-x86_64.c
@@ -62,4 +62,4 @@
 // CHECK: declare i32 @toupper(i32) [[NUW_RO:#[0-9]+]]
 
 // CHECK: attributes [[NUW_RO]] = { nounwind readonly{{.*}} }
-// CHECK: attributes [[NUW_RO_CALL]] = { nounwind readonly }
+// CHECK: attributes [[NUW_RO_CALL]] = { nounwind readonly willreturn }