Add a Context::emit_to_memory function.

This function will emit the binary machine code into contiguous raw
memory while sending relocations to a RelocSink.

Add a MemoryCodeSink for generating machine code directly into memory
efficiently. Allow the TargetIsa to provide emit_function
implementations that are specialized to the MemoryCodeSink type to avoid
needless small virtual callbacks to put1() et etc.

lib/cretonne/src/isa/intel/mod.rs

@@ -6,7 +6,7 @@ mod binemit;
 mod enc_tables;
 mod registers;
 
-use binemit::CodeSink;
+use binemit::{CodeSink, MemoryCodeSink, emit_function};
 use super::super::settings as shared_settings;
 use isa::enc_tables::{self as shared_enc_tables, lookup_enclist, Encodings};
 use isa::Builder as IsaBuilder;
@@ -95,6 +95,10 @@ impl TargetIsa for Isa {
         binemit::emit_inst(func, inst, sink)
     }
 
+    fn emit_function(&self, func: &ir::Function, sink: &mut MemoryCodeSink) {
+        emit_function(func, binemit::emit_inst, sink)
+    }
+
     fn reloc_names(&self) -> &'static [&'static str] {
         &binemit::RELOC_NAMES
     }