diff --git a/src/librustc_codegen_llvm/common.rs b/src/librustc_codegen_llvm/common.rs
index 0d0ee2f6a150e..a1a5232d58832 100644
--- a/src/librustc_codegen_llvm/common.rs
+++ b/src/librustc_codegen_llvm/common.rs
@@ -2,7 +2,7 @@
 
 //! Code that is useful in various codegen modules.
 
-use crate::llvm::{self, True, False, Bool, BasicBlock, OperandBundleDef};
+use crate::llvm::{self, True, False, Bool, BasicBlock, OperandBundleDef, ConstantInt};
 use crate::abi;
 use crate::consts;
 use crate::type_::Type;
@@ -246,30 +246,22 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     }
 
     fn const_to_opt_uint(&self, v: &'ll Value) -> Option<u64> {
-        if is_const_integral(v) {
-            unsafe {
-                Some(llvm::LLVMConstIntGetZExtValue(v))
-            }
-        } else {
-            None
-        }
+        try_as_const_integral(v).map(|v| unsafe {
+            llvm::LLVMConstIntGetZExtValue(v)
+        })
     }
 
     fn const_to_opt_u128(&self, v: &'ll Value, sign_ext: bool) -> Option<u128> {
-        unsafe {
-            if is_const_integral(v) {
-                let (mut lo, mut hi) = (0u64, 0u64);
-                let success = llvm::LLVMRustConstInt128Get(v, sign_ext,
-                                                           &mut hi, &mut lo);
-                if success {
-                    Some(hi_lo_to_u128(lo, hi))
-                } else {
-                    None
-                }
+        try_as_const_integral(v).and_then(|v| unsafe {
+            let (mut lo, mut hi) = (0u64, 0u64);
+            let success = llvm::LLVMRustConstInt128Get(v, sign_ext,
+                                                        &mut hi, &mut lo);
+            if success {
+                Some(hi_lo_to_u128(lo, hi))
             } else {
                 None
             }
-        }
+        })
     }
 
     fn scalar_to_backend(
@@ -387,8 +379,8 @@ fn hi_lo_to_u128(lo: u64, hi: u64) -> u128 {
     ((hi as u128) << 64) | (lo as u128)
 }
 
-fn is_const_integral(v: &'ll Value) -> bool {
+fn try_as_const_integral(v: &'ll Value) -> Option<&'ll ConstantInt> {
     unsafe {
-        llvm::LLVMIsAConstantInt(v).is_some()
+        llvm::LLVMIsAConstantInt(v)
     }
 }
diff --git a/src/librustc_codegen_llvm/llvm/ffi.rs b/src/librustc_codegen_llvm/llvm/ffi.rs
index b07214fdc03f3..a2313b933a6c9 100644
--- a/src/librustc_codegen_llvm/llvm/ffi.rs
+++ b/src/librustc_codegen_llvm/llvm/ffi.rs
@@ -510,6 +510,7 @@ extern { pub type Module; }
 extern { pub type Context; }
 extern { pub type Type; }
 extern { pub type Value; }
+extern { pub type ConstantInt; }
 extern { pub type Metadata; }
 extern { pub type BasicBlock; }
 #[repr(C)]
@@ -719,8 +720,8 @@ extern "C" {
     pub fn LLVMConstInt(IntTy: &Type, N: c_ulonglong, SignExtend: Bool) -> &Value;
     pub fn LLVMConstIntOfArbitraryPrecision(IntTy: &Type, Wn: c_uint, Ws: *const u64) -> &Value;
     pub fn LLVMConstReal(RealTy: &Type, N: f64) -> &Value;
-    pub fn LLVMConstIntGetZExtValue(ConstantVal: &Value) -> c_ulonglong;
-    pub fn LLVMRustConstInt128Get(ConstantVal: &Value, SExt: bool,
+    pub fn LLVMConstIntGetZExtValue(ConstantVal: &ConstantInt) -> c_ulonglong;
+    pub fn LLVMRustConstInt128Get(ConstantVal: &ConstantInt, SExt: bool,
                                   high: &mut u64, low: &mut u64) -> bool;
 
 
@@ -1666,7 +1667,7 @@ extern "C" {
     #[allow(improper_ctypes)]
     pub fn LLVMRustWriteValueToString(value_ref: &Value, s: &RustString);
 
-    pub fn LLVMIsAConstantInt(value_ref: &Value) -> Option<&Value>;
+    pub fn LLVMIsAConstantInt(value_ref: &Value) -> Option<&ConstantInt>;
 
     pub fn LLVMRustPassKind(Pass: &Pass) -> PassKind;
     pub fn LLVMRustFindAndCreatePass(Pass: *const c_char) -> Option<&'static mut Pass>;