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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112567 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 34c484103cfc5b311ee232432c0990c670ca89d5..5dd5fdb7b1595105ab968ae707c1083159c0176f 100644 (file)
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/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.