[globalisel][tblgen] Add support for iPTR and implement am_unscaled* and am_indexed*

Summary:
iPTR is a pointer of subtarget-specific size to any address space. Therefore
type checks on this size derive the SizeInBits from a subtarget hook.

At this point, we can import the simplests G_LOAD rules and select load
instructions using them. Further patches will support for the predicates to
enable additional loads as well as the stores.

Depends on D37457

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

Reviewed By: qcolombet

Subscribers: kristof.beyls, javed.absar, llvm-commits, igorb

Differential Revision: https://reviews.llvm.org/D37458

llvm-svn: 315885

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp b/llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
index e4ee2bb7cf4..2a563c9bf5c 100644
--- a/llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/InstructionSelector.cpp
@@ -18,6 +18,7 @@
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/MC/MCInstrDesc.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
@@ -98,6 +99,23 @@ bool InstructionSelector::isOperandImmEqual(
   return false;
 }
 
+bool InstructionSelector::isBaseWithConstantOffset(
+    const MachineOperand &Root, const MachineRegisterInfo &MRI) const {
+  if (!Root.isReg())
+    return false;
+
+  MachineInstr *RootI = MRI.getVRegDef(Root.getReg());
+  if (RootI->getOpcode() != TargetOpcode::G_GEP)
+    return false;
+
+  MachineOperand &RHS = RootI->getOperand(2);
+  MachineInstr *RHSI = MRI.getVRegDef(RHS.getReg());
+  if (RHSI->getOpcode() != TargetOpcode::G_CONSTANT)
+    return false;
+
+  return true;
+}
+
 bool InstructionSelector::isObviouslySafeToFold(MachineInstr &MI) const {
   return !MI.mayLoadOrStore() && !MI.hasUnmodeledSideEffects() &&
          MI.implicit_operands().begin() == MI.implicit_operands().end();