[AArch64] Add AArch64Subtarget::isFusion function.

Summary:
isFusion returns true if the subtarget supports any kind of instruction
fusion, similar to ARMSubtarget::isFusion. This was suggested in D34142.

This changes the current behavior slightly, because the macro fusion mutation 
is now added to the PostRA MachineScheduler in case the subtarget supports
any kind of fusion. I think that makes sense because if the PostRA 
MachineScheduler is run, there is potential that instructions scheduled back to 
back are re-scheduled.

Reviewers: evandro, t.p.northover, joelkevinjones, joel_k_jones, steleman

Reviewed By: joelkevinjones

Subscribers: joel_k_jones, aemerson, rengolin, javed.absar, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D34958

llvm-svn: 307842

2 files changed, 8 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64Subtarget.h b/llvm/lib/Target/AArch64/AArch64Subtarget.h
index 7933e58c49e..db53946cbc7 100644
--- a/llvm/lib/Target/AArch64/AArch64Subtarget.h
+++ b/llvm/lib/Target/AArch64/AArch64Subtarget.h
@@ -218,6 +218,13 @@ public:
   bool hasArithmeticCbzFusion() const { return HasArithmeticCbzFusion; }
   bool hasFuseAES() const { return HasFuseAES; }
   bool hasFuseLiterals() const { return HasFuseLiterals; }
+
+  /// \brief Return true if the CPU supports any kind of instruction fusion.
+  bool hasFusion() const {
+    return hasArithmeticBccFusion() || hasArithmeticCbzFusion() ||
+           hasFuseAES() || hasFuseLiterals();
+  }
+
   bool useRSqrt() const { return UseRSqrt; }
   unsigned getMaxInterleaveFactor() const { return MaxInterleaveFactor; }
   unsigned getVectorInsertExtractBaseCost() const {
diff --git a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
index 1252f940381..25bcc79b349 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -287,7 +287,7 @@ public:
   ScheduleDAGInstrs *
   createPostMachineScheduler(MachineSchedContext *C) const override {
     const AArch64Subtarget &ST = C->MF->getSubtarget<AArch64Subtarget>();
-    if (ST.hasFuseAES() || ST.hasFuseLiterals()) {
+    if (ST.hasFusion()) {
       // Run the Macro Fusion after RA again since literals are expanded from
       // pseudos then (v. addPreSched2()).
       ScheduleDAGMI *DAG = createGenericSchedPostRA(C);