[DFAPacketizer] Reapply: Track resources for packetized instructions

Reapply with fix to reduce resources required by the compiler - use
unsigned[2] instead of std::pair. This causes clang and gcc to compile
the generated file multiple times faster, and hopefully will reduce
the resource requirements on Visual Studio also. This fix is a little
ugly but it's clearly the same issue the previous author of
DFAPacketizer faced (the previous tables use unsigned[2] rather uglily
too).

This patch allows the DFAPacketizer to be queried after a packet is formed to work out which
resources were allocated to the packetized instructions.

This is particularly important for targets that do their own bundle packing - it's not
sufficient to know simply that instructions can share a packet; which slots are used is
also required for encoding.

This extends the emitter to emit a side-table containing resource usage diffs for each
state transition. The packetizer maintains a set of all possible resource states in its
current state. After packetization is complete, all remaining resource states are
possible packetization strategies.

The sidetable is only ~500K for Hexagon, but the extra tracking is disabled by default
(most uses of the packetizer like MachinePipeliner don't care and don't need the extra
maintained state).

Differential Revision: https://reviews.llvm.org/D66936

llvm-svn: 371399

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp b/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp
index c89c0b3369f..7024dafd479 100644
--- a/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp
@@ -24,6 +24,7 @@
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
@@ -1763,6 +1764,16 @@ HexagonPacketizerList::addToPacket(MachineInstr &MI) {
 void HexagonPacketizerList::endPacket(MachineBasicBlock *MBB,
                                       MachineBasicBlock::iterator EndMI) {
   // Replace VLIWPacketizerList::endPacket(MBB, EndMI).
+  LLVM_DEBUG({
+    if (!CurrentPacketMIs.empty()) {
+      dbgs() << "Finalizing packet:\n";
+      unsigned Idx = 0;
+      for (MachineInstr *MI : CurrentPacketMIs) {
+        unsigned R = ResourceTracker->getUsedResources(Idx++);
+        dbgs() << " * [res:0x" << utohexstr(R) << "] " << *MI;
+      }
+    }
+  });
 
   bool memShufDisabled = getmemShufDisabled();
   if (memShufDisabled && !foundLSInPacket()) {