[globalisel][tablegen] Revise API for ComplexPattern operands to improve flexibility.

Summary:
Some targets need to be able to do more complex rendering than just adding an
operand or two to an instruction. For example, it may need to insert an
instruction to extract a subreg first, or it may need to perform an operation
on the operand.

In SelectionDAG, targets would create SDNode's to achieve the desired effect
during the complex pattern predicate. This worked because SelectionDAG had a
form of garbage collection that would take care of SDNode's that were created
but not used due to a later predicate rejecting a match. This doesn't translate
well to GlobalISel and the churn was wasteful.

The API changes in this patch enable GlobalISel to accomplish the same thing
without the waste. The API is now:
	InstructionSelector::OptionalComplexRendererFn selectArithImmed(MachineOperand &Root) const;
where Root is the root of the match. The return value can be omitted to
indicate that the predicate failed to match, or a function with the signature
ComplexRendererFn can be returned. For example:
	return OptionalComplexRendererFn(
	       [=](MachineInstrBuilder &MIB) { MIB.addImm(Immed).addImm(ShVal); });
adds two immediate operands to the rendered instruction. Immed and ShVal are
captured from the predicate function.

As an added bonus, this also reduces the amount of information we need to
provide to GIComplexOperandMatcher.

Depends on D31418

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

Reviewed By: ab

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

Differential Revision: https://reviews.llvm.org/D31761

llvm-svn: 301079

3 files changed, 10 insertions, 17 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 16be4432b16..c44daf306ea 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -693,11 +693,11 @@ def addsub_shifted_imm32_neg : addsub_shifted_imm_neg<i32>;
 def addsub_shifted_imm64_neg : addsub_shifted_imm_neg<i64>;
 
 def gi_addsub_shifted_imm32 :
-    GIComplexOperandMatcher<s32, (ops i32imm, i32imm), "selectArithImmed">,
+    GIComplexOperandMatcher<s32, "selectArithImmed">,
     GIComplexPatternEquiv<addsub_shifted_imm32>;
 
 def gi_addsub_shifted_imm64 :
-    GIComplexOperandMatcher<s64, (ops i32imm, i32imm), "selectArithImmed">,
+    GIComplexOperandMatcher<s64, "selectArithImmed">,
     GIComplexPatternEquiv<addsub_shifted_imm64>;
 
 class neg_addsub_shifted_imm<ValueType Ty>
diff --git a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
index d2043823762..b0e0e3eb4ba 100644
--- a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -67,8 +67,7 @@ private:
   bool selectCompareBranch(MachineInstr &I, MachineFunction &MF,
                            MachineRegisterInfo &MRI) const;
 
-  bool selectArithImmed(MachineOperand &Root, MachineOperand &Result1,
-                        MachineOperand &Result2) const;
+  ComplexRendererFn selectArithImmed(MachineOperand &Root) const;
 
   const AArch64TargetMachine &TM;
   const AArch64Subtarget &STI;
@@ -1329,9 +1328,8 @@ bool AArch64InstructionSelector::select(MachineInstr &I) const {
 /// SelectArithImmed - Select an immediate value that can be represented as
 /// a 12-bit value shifted left by either 0 or 12.  If so, return true with
 /// Val set to the 12-bit value and Shift set to the shifter operand.
-bool AArch64InstructionSelector::selectArithImmed(
-    MachineOperand &Root, MachineOperand &Result1,
-    MachineOperand &Result2) const {
+InstructionSelector::ComplexRendererFn
+AArch64InstructionSelector::selectArithImmed(MachineOperand &Root) const {
   MachineInstr &MI = *Root.getParent();
   MachineBasicBlock &MBB = *MI.getParent();
   MachineFunction &MF = *MBB.getParent();
@@ -1350,13 +1348,13 @@ bool AArch64InstructionSelector::selectArithImmed(
   else if (Root.isReg()) {
     MachineInstr *Def = MRI.getVRegDef(Root.getReg());
     if (Def->getOpcode() != TargetOpcode::G_CONSTANT)
-      return false;
+      return nullptr;
     MachineOperand &Op1 = Def->getOperand(1);
     if (!Op1.isCImm() || Op1.getCImm()->getBitWidth() > 64)
-      return false;
+      return nullptr;
     Immed = Op1.getCImm()->getZExtValue();
   } else
-    return false;
+    return nullptr;
 
   unsigned ShiftAmt;
 
@@ -1366,14 +1364,10 @@ bool AArch64InstructionSelector::selectArithImmed(
     ShiftAmt = 12;
     Immed = Immed >> 12;
   } else
-    return false;
+    return nullptr;
 
   unsigned ShVal = AArch64_AM::getShifterImm(AArch64_AM::LSL, ShiftAmt);
-  Result1.ChangeToImmediate(Immed);
-  Result1.clearParent();
-  Result2.ChangeToImmediate(ShVal);
-  Result2.clearParent();
-  return true;
+  return [=](MachineInstrBuilder &MIB) { MIB.addImm(Immed).addImm(ShVal); };
 }
 
 namespace llvm {
diff --git a/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp b/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
index e0aecff2633..78a9144bd32 100644
--- a/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
+++ b/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
@@ -661,7 +661,6 @@ static bool IsAnAddressOperand(const MachineOperand &MO) {
     return false;
   case MachineOperand::MO_IntrinsicID:
   case MachineOperand::MO_Predicate:
-  case MachineOperand::MO_Placeholder:
     llvm_unreachable("should not exist post-isel");
   }
   llvm_unreachable("unhandled machine operand type");