[PATCH] D40177: performance improvements for ThunderX2 T99

[Stefan Teleman via Phabricator via llvm-commits]

steleman created this revision.
Herald added a subscriber: javed.absar.

This changeset causes performance improvements for the Cavium ThunderX2T99 micro-arch. The changeset is specific to T99. It does not affect any other micro-arch.

Tested with SPECcpu2017 and libquantum.

As an example, for the performance gains on libquantum, please see here:

https://docs.google.com/spreadsheets/d/1Lo1o2E1NjrpkwS7DvYYWsiVvPdd93h7KBaqeptMrZPY/edit?usp=sharing


Repository:
  rL LLVM

https://reviews.llvm.org/D40177

Files:
  lib/Target/AArch64/AArch64ISelLowering.cpp
  lib/Target/AArch64/AArch64ISelLowering.h
  lib/Target/AArch64/AArch64SchedThunderX2T99.td


Index: lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- lib/Target/AArch64/AArch64ISelLowering.cpp
+++ lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -10978,6 +10978,11 @@
   return OptSize && !VT.isVector();
 }
 
+bool AArch64TargetLowering::enableAggressiveFMAFusion(EVT VT) const {
+  return Subtarget->getProcFamily() == AArch64Subtarget::ThunderX2T99 &&
+    VT.isFloatingPoint();
+}
+
 unsigned
 AArch64TargetLowering::getVaListSizeInBits(const DataLayout &DL) const {
   if (Subtarget->isTargetDarwin() || Subtarget->isTargetWindows())
Index: lib/Target/AArch64/AArch64ISelLowering.h
===================================================================
--- lib/Target/AArch64/AArch64ISelLowering.h
+++ lib/Target/AArch64/AArch64ISelLowering.h
@@ -455,6 +455,9 @@
     return true;
   }
 
+  /// Enable aggressive FMA fusion on targets that want it.
+  bool enableAggressiveFMAFusion(EVT VT) const override;
+
   /// Returns the size of the platform's va_list object.
   unsigned getVaListSizeInBits(const DataLayout &DL) const override;
 
Index: lib/Target/AArch64/AArch64SchedThunderX2T99.td
===================================================================
--- lib/Target/AArch64/AArch64SchedThunderX2T99.td
+++ lib/Target/AArch64/AArch64SchedThunderX2T99.td
@@ -22,7 +22,7 @@
   let LoadLatency           =   4; // Optimistic load latency.
   let MispredictPenalty     =  12; // Extra cycles for mispredicted branch.
   // Determined via a mix of micro-arch details and experimentation.
-  let LoopMicroOpBufferSize =  32;
+  let LoopMicroOpBufferSize =  128;
   let PostRAScheduler       =   1; // Using PostRA sched.
   let CompleteModel         =   1;
 
@@ -391,7 +391,8 @@
 def : WriteRes<WriteHint,    []> { let Latency = 1; }
 
 def : WriteRes<WriteAtomic,  []> {
-  let Unsupported = 1;
+  let Unsupported = 0;
+  let Latency = 4;
   let NumMicroOps = 2;
 }
 


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