[globalisel] Decouple src pattern operands from dst pattern operands.

Summary:
This isn't testable for AArch64 by itself so this patch also adds
support for constant immediates in the pattern and physical
register uses in the result.

The new IntOperandMatcher matches the constant in patterns such as
'(set $rd:GPR32, (G_XOR $rs:GPR32, -1))'. It's always safe to fold
immediates into an instruction so this is the first rule that will match
across multiple BB's.

The Renderer hierarchy is responsible for adding operands to the result
instruction. Renderers can copy operands (CopyRenderer) or add physical
registers (in particular %wzr and %xzr) to the result instruction
in any order (OperandMatchers now import the operand names from
SelectionDAG to allow renderers to access any operand). This allows us to
emit the result instruction for:
  %1 = G_XOR %0, -1 --> %1 = ORNWrr %wzr, %0
  %1 = G_XOR -1, %0 --> %1 = ORNWrr %wzr, %0
although the latter is untested since the matcher/importer has not been
taught about commutativity yet.

Added BuildMIAction which can build new instructions and mutate them where
possible. W.r.t the mutation aspect, MatchActions are now told the name of
an instruction they can recycle and BuildMIAction will emit mutation code
when the renderers are appropriate. They are appropriate when all operands
are rendered using CopyRenderer and the indices are the same as the matcher.
This currently assumes that all operands have at least one matcher.

Finally, this change also fixes a crash in
AArch64InstructionSelector::select() caused by an immediate operand
passing isImm() rather than isCImm(). This was uncovered by the other
changes and was detected by existing tests.

Depends on D29711

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

Reviewed By: rovka

Subscribers: aemerson, dberris, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D29712

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296131 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/Target/AArch64/AArch64InstructionSelector.cpp b/lib/Target/AArch64/AArch64InstructionSelector.cpp
index f83c7f0e6cc..1656b5c6efc 100644
--- a/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ b/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -634,9 +634,12 @@ bool AArch64InstructionSelector::select(MachineInstr &I) const {
       // FIXME: Is going through int64_t always correct?
       ImmOp.ChangeToImmediate(
           ImmOp.getFPImm()->getValueAPF().bitcastToAPInt().getZExtValue());
-    } else {
+    } else if (I.getOperand(1).isCImm()) {
       uint64_t Val = I.getOperand(1).getCImm()->getZExtValue();
       I.getOperand(1).ChangeToImmediate(Val);
+    } else if (I.getOperand(1).isImm()) {
+      uint64_t Val = I.getOperand(1).getImm();
+      I.getOperand(1).ChangeToImmediate(Val);
     }
 
     constrainSelectedInstRegOperands(I, TII, TRI, RBI);