codegen_llvm: fix spelling & grammatical errors

src/librustc_codegen_llvm/abi.rs

@@ -336,7 +336,7 @@ impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
             RustIntrinsic | PlatformIntrinsic |
             Rust | RustCall => Conv::C,
 
-            // It's the ABI's job to select this, not us.
+            // It's the ABI's job to select this, not ours.
             System => bug!("system abi should be selected elsewhere"),
 
             Stdcall => Conv::X86Stdcall,

src/librustc_codegen_llvm/base.rs

@@ -363,8 +363,8 @@ fn cast_shift_rhs<'ll, F, G>(op: hir::BinOpKind,
         if lhs_sz < rhs_sz {
             trunc(rhs, lhs_llty)
         } else if lhs_sz > rhs_sz {
-            // FIXME (#1877: If shifting by negative
-            // values becomes not undefined then this is wrong.
+            // FIXME (#1877: If in the future shifting by negative
+            // values is no longer undefined then this is wrong.
             zext(rhs, lhs_llty)
         } else {
             rhs

src/librustc_codegen_llvm/value.rs

@@ -34,6 +34,6 @@ impl fmt::Debug for Value {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str(&llvm::build_string(|s| unsafe {
             llvm::LLVMRustWriteValueToString(self, s);
-        }).expect("nun-UTF8 value description from LLVM"))
+        }).expect("non-UTF8 value description from LLVM"))
     }
 }