[DFAPacketizer] Allow up to 64 functional units

Summary:
To drive the automaton we used a uint64_t as an action type. This
contained the transition's resource requirements as a conjunction:

  (a OR b) AND (b OR c)

We encoded this conjunction as a sequence of four 16-bit bitmasks.
This limited the number of addressable functional units to 16, which
is quite low and has bitten many people in the past.

Instead, the DFAEmitter now generates a lookup table from InstrItinerary
class (index of the ItinData inside the ProcItineraries) to an internal
action index which is essentially a dense embedding of the conjunctive
form. Because we never materialize the conjunctive form, we no longer
have the 16 FU restriction.

In this patch we limit to 64 functional units due to using a uint64_t
bitmask in the DFAEmitter. Now that we've decoupled these representations
we can increase this in future.

Reviewers: ThomasRaoux, kparzysz, majnemer

Reviewed By: ThomasRaoux

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69110

1 files changed, 8 insertions, 54 deletions

diff --git a/llvm/lib/CodeGen/DFAPacketizer.cpp b/llvm/lib/CodeGen/DFAPacketizer.cpp
index a169c3cb16b..afcf014bca4 100644
--- a/llvm/lib/CodeGen/DFAPacketizer.cpp
+++ b/llvm/lib/CodeGen/DFAPacketizer.cpp
@@ -52,68 +52,22 @@ static cl::opt<unsigned> InstrLimit("dfa-instr-limit", cl::Hidden,
 
 static unsigned InstrCount = 0;
 
-// --------------------------------------------------------------------
-// Definitions shared between DFAPacketizer.cpp and DFAPacketizerEmitter.cpp
-
-static DFAInput addDFAFuncUnits(DFAInput Inp, unsigned FuncUnits) {
-  return (Inp << DFA_MAX_RESOURCES) | FuncUnits;
-}
-
-/// Return the DFAInput for an instruction class input vector.
-/// This function is used in both DFAPacketizer.cpp and in
-/// DFAPacketizerEmitter.cpp.
-static DFAInput getDFAInsnInput(const std::vector<unsigned> &InsnClass) {
-  DFAInput InsnInput = 0;
-  assert((InsnClass.size() <= DFA_MAX_RESTERMS) &&
-         "Exceeded maximum number of DFA terms");
-  for (auto U : InsnClass)
-    InsnInput = addDFAFuncUnits(InsnInput, U);
-  return InsnInput;
-}
-
-// --------------------------------------------------------------------
-
-// Make sure DFA types are large enough for the number of terms & resources.
-static_assert((DFA_MAX_RESTERMS * DFA_MAX_RESOURCES) <=
-              (8 * sizeof(DFAInput)),
-              "(DFA_MAX_RESTERMS * DFA_MAX_RESOURCES) too big for DFAInput");
-static_assert(
-    (DFA_MAX_RESTERMS * DFA_MAX_RESOURCES) <= (8 * sizeof(DFAStateInput)),
-    "(DFA_MAX_RESTERMS * DFA_MAX_RESOURCES) too big for DFAStateInput");
-
-// Return the DFAInput for an instruction class.
-DFAInput DFAPacketizer::getInsnInput(unsigned InsnClass) {
-  // Note: this logic must match that in DFAPacketizerDefs.h for input vectors.
-  DFAInput InsnInput = 0;
-  unsigned i = 0;
-  (void)i;
-  for (const InstrStage *IS = InstrItins->beginStage(InsnClass),
-       *IE = InstrItins->endStage(InsnClass); IS != IE; ++IS) {
-    InsnInput = addDFAFuncUnits(InsnInput, IS->getUnits());
-    assert((i++ < DFA_MAX_RESTERMS) && "Exceeded maximum number of DFA inputs");
-  }
-  return InsnInput;
-}
-
-// Return the DFAInput for an instruction class input vector.
-DFAInput DFAPacketizer::getInsnInput(const std::vector<unsigned> &InsnClass) {
-  return getDFAInsnInput(InsnClass);
-}
-
 // Check if the resources occupied by a MCInstrDesc are available in the
 // current state.
 bool DFAPacketizer::canReserveResources(const MCInstrDesc *MID) {
-  unsigned InsnClass = MID->getSchedClass();
-  DFAInput InsnInput = getInsnInput(InsnClass);
-  return A.canAdd(InsnInput);
+  unsigned Action = ItinActions[MID->getSchedClass()];
+  if (MID->getSchedClass() == 0 || Action == 0)
+    return false;
+  return A.canAdd(Action);
 }
 
 // Reserve the resources occupied by a MCInstrDesc and change the current
 // state to reflect that change.
 void DFAPacketizer::reserveResources(const MCInstrDesc *MID) {
-  unsigned InsnClass = MID->getSchedClass();
-  DFAInput InsnInput = getInsnInput(InsnClass);
-  A.add(InsnInput);
+  unsigned Action = ItinActions[MID->getSchedClass()];
+  if (MID->getSchedClass() == 0 || Action == 0)
+    return;
+  A.add(Action);
 }
 
 // Check if the resources occupied by a machine instruction are available