Teach machine cse to commute instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121903 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index 0143d0f..fc3f594 100644
--- a/lib/CodeGen/MachineCSE.cpp
+++ b/lib/CodeGen/MachineCSE.cpp
@@ -24,7 +24,6 @@
#include "llvm/ADT/ScopedHashTable.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
@@ -33,6 +32,7 @@
STATISTIC(NumCSEs, "Number of common subexpression eliminated");
STATISTIC(NumPhysCSEs,
"Number of physreg referencing common subexpr eliminated");
+STATISTIC(NumCommutes, "Number of copies coalesced after commuting");
namespace {
class MachineCSE : public MachineFunctionPass {
@@ -368,7 +368,22 @@
FoundCSE = VNT.count(MI);
}
}
- // FIXME: commute commutable instructions?
+
+ // Commute commutable instructions.
+ bool Commuted = false;
+ if (!FoundCSE && MI->getDesc().isCommutable()) {
+ MachineInstr *NewMI = TII->commuteInstruction(MI);
+ if (NewMI) {
+ Commuted = true;
+ FoundCSE = VNT.count(NewMI);
+ if (NewMI != MI)
+ // New instruction. It doesn't need to be kept.
+ NewMI->eraseFromParent();
+ else if (!FoundCSE)
+ // MI was changed but it didn't help, commute it back!
+ (void)TII->commuteInstruction(MI);
+ }
+ }
// If the instruction defines physical registers and the values *may* be
// used, then it's not safe to replace it with a common subexpression.
@@ -430,6 +445,8 @@
++NumCSEs;
if (!PhysRefs.empty())
++NumPhysCSEs;
+ if (Commuted)
+ ++NumCommutes;
} else {
DEBUG(dbgs() << "*** Not profitable, avoid CSE!\n");
VNT.insert(MI, CurrVN++);