Add experimental -disable-physical-join command line option.

Eventually, we want to disable physreg coalescing completely, and let the
register allocator do its job using hints.

This option makes it possible to measure the impact of disabling physreg
coalescing.

llvm-svn: 112567

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 34c484103cf..5dd5fdb7b15 100644
--- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -59,6 +59,11 @@ DisableCrossClassJoin("disable-cross-class-join",
                cl::desc("Avoid coalescing cross register class copies"),
                cl::init(false), cl::Hidden);
 
+static cl::opt<bool>
+DisablePhysicalJoin("disable-physical-join",
+               cl::desc("Avoid coalescing physical register copies"),
+               cl::init(false), cl::Hidden);
+
 INITIALIZE_AG_PASS(SimpleRegisterCoalescing, RegisterCoalescer,
                 "simple-register-coalescing", "Simple Register Coalescing", 
                 false, false, true);
@@ -1036,6 +1041,11 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
     return false;  // Not coalescable.
   }
 
+  if (DisablePhysicalJoin && CP.isPhys()) {
+    DEBUG(dbgs() << "\tPhysical joins disabled.\n");
+    return false;
+  }
+
   DEBUG(dbgs() << "\tConsidering merging %reg" << CP.getSrcReg());
 
   // Enforce policies.