DAG->DAG instruction selection for ia64! "hello world" works, not much else.

use -enable-ia64-dag-isel to turn this on

TODO: delete lowering stuff from the pattern isel
    : get operations on predicate bits working
    : get other bits of pseudocode going
    : use sampo's mulh/mull-using divide-by-constant magic
    : *so* many patterns ("extr", "tbit" and "dep" will be fun :)
    : add FP
    : add a JIT!
    : get it working 100%

in short: this'll be happier in a couple of weeks, but it's here now so
the tester can make me feel guilty sooner.

OTHER: there are a couple of fixes to the pattern isel, in particular
making the linker happy with big blobs of fun like pypy.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24058 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/IA64/IA64TargetMachine.cpp

@@ -37,6 +37,9 @@ namespace {
                               cl::desc("Disable the IA64 asm printer, for use "
                                        "when profiling the code generator."));
 
+  cl::opt<bool> EnableDAGIsel("enable-ia64-dag-isel", cl::Hidden,
+		              cl::desc("Enable the IA64 DAG->DAG isel"));
+
   // Register the target.
   RegisterTarget<IA64TargetMachine> X("ia64", "  IA-64 (Itanium)");
 }
@@ -97,8 +100,12 @@ bool IA64TargetMachine::addPassesToEmitFile(PassManager &PM,
   // Make sure that no unreachable blocks are instruction selected.
   PM.add(createUnreachableBlockEliminationPass());
 
-  PM.add(createIA64PatternInstructionSelector(*this));
-
+  // Add an instruction selector
+  if(EnableDAGIsel)
+    PM.add(createIA64DAGToDAGInstructionSelector(*this));
+  else
+    PM.add(createIA64PatternInstructionSelector(*this));
+  
 /* XXX not yet. ;)
   // Run optional SSA-based machine code optimizations next...
   if (!NoSSAPeephole)