[globalisel][tablegen] Compute available feature bits correctly.

Summary:
Predicate<> now has a field to indicate how often it must be recomputed.
Currently, there are two frequencies, per-module (RecomputePerFunction==0)
and per-function (RecomputePerFunction==1). Per-function predicates are
currently recomputed more frequently than necessary since the only predicate
in this category is cheap to test. Per-module predicates are now computed in
getSubtargetImpl() while per-function predicates are computed in selectImpl().

Tablegen now manages the PredicateBitset internally. It should only be
necessary to add the required includes.

Also fixed a problem revealed by the test case where
constrainSelectedInstRegOperands() would attempt to tie operands that
BuildMI had already tied.

Reviewers: ab, qcolombet, t.p.northover, rovka, aditya_nandakumar

Reviewed By: rovka

Subscribers: kristof.beyls, igorb, llvm-commits

Differential Revision: https://reviews.llvm.org/D32491

llvm-svn: 301750

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp b/llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
index 942680b6fff..c67da8629a3 100644
--- a/llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
@@ -58,10 +58,11 @@ bool InstructionSelector::constrainSelectedInstRegOperands(
     MO.setReg(constrainOperandRegClass(MF, TRI, MRI, TII, RBI, I, I.getDesc(),
                                        Reg, OpI));
 
-    // Tie uses to defs as indicated in MCInstrDesc.
+    // Tie uses to defs as indicated in MCInstrDesc if this hasn't already been
+    // done.
     if (MO.isUse()) {
       int DefIdx = I.getDesc().getOperandConstraint(OpI, MCOI::TIED_TO);
-      if (DefIdx != -1)
+      if (DefIdx != -1 && !I.isRegTiedToUseOperand(DefIdx))
         I.tieOperands(DefIdx, OpI);
     }
   }