calls can be supported.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57428 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/FastISel.cpp

@@ -11,30 +11,30 @@
 //
 // "Fast" instruction selection is designed to emit very poor code quickly.
 // Also, it is not designed to be able to do much lowering, so most illegal
-// types (e.g. i64 on 32-bit targets) and operations (e.g. calls) are not
+// types (e.g. i64 on 32-bit targets) and operations are not supported.  It is
-// supported. It is also not intended to be able to do much optimization,
+// also not intended to be able to do much optimization, except in a few cases
-// except in a few cases where doing optimizations reduces overall compile
+// where doing optimizations reduces overall compile time.  For example, folding
-// time (e.g. folding constants into immediate fields, because it's cheap
+// constants into immediate fields is often done, because it's cheap and it
-// and it reduces the number of instructions later phases have to examine).
+// reduces the number of instructions later phases have to examine.
 //
 // "Fast" instruction selection is able to fail gracefully and transfer
 // control to the SelectionDAG selector for operations that it doesn't
-// support. In many cases, this allows us to avoid duplicating a lot of
+// support.  In many cases, this allows us to avoid duplicating a lot of
 // the complicated lowering logic that SelectionDAG currently has.
 //
 // The intended use for "fast" instruction selection is "-O0" mode
 // compilation, where the quality of the generated code is irrelevant when
-// weighed against the speed at which the code can be generated. Also,
+// weighed against the speed at which the code can be generated.  Also,
 // at -O0, the LLVM optimizers are not running, and this makes the
 // compile time of codegen a much higher portion of the overall compile
-// time. Despite its limitations, "fast" instruction selection is able to
+// time.  Despite its limitations, "fast" instruction selection is able to
 // handle enough code on its own to provide noticeable overall speedups
 // in -O0 compiles.
 //
 // Basic operations are supported in a target-independent way, by reading
 // the same instruction descriptions that the SelectionDAG selector reads,
 // and identifying simple arithmetic operations that can be directly selected
-// from simple operators. More complicated operations currently require
+// from simple operators.  More complicated operations currently require
 // target-specific code.
 //
 //===----------------------------------------------------------------------===//