[GlobalISel][Legalizer] More concise and faster widenScalar, NFC

Refactoring LegalizerHelper::widenScalar member function reducing its
size by approximately a factor of 2 and (hopefuly) making it more
straightforward and regular by introducing widenScalarSrc and
widenScalarDst helper methods.

The new widenScalar* methods mutate the instructions in place instead
of recreating them from scratch and removing the originals. The
compile time implications of this were measured on sqlite3
amalgamation, targeting AArch64 in -O0:

LegalizerHelper::widenScalar: > 25% faster
Legalizer::runOnMachineFunction: ~ 4.0 - 4.5% faster

Also adding MachineOperand::setCImm and refactoring out
MachineIRBuilder::recordInsertion methods to make the change possible.

Reviewers: aditya_nandakumar, bogner, javed.absar, t.p.northover, ab, dsanders, arsenm

Reviewed By: aditya_nandakumar

Subscribers: wdng, rovka, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D46414

llvm-svn: 331819

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 273044b..a3bf45f 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -53,6 +53,11 @@ void MachineIRBuilderBase::setInsertPt(MachineBasicBlock &MBB,
   State.II = II;
 }
 
+void MachineIRBuilderBase::recordInsertion(MachineInstr *InsertedInstr) const {
+  if (State.InsertedInstr)
+    State.InsertedInstr(InsertedInstr);
+}
+
 void MachineIRBuilderBase::recordInsertions(
     std::function<void(MachineInstr *)> Inserted) {
   State.InsertedInstr = std::move(Inserted);
@@ -77,8 +82,7 @@ MachineInstrBuilder MachineIRBuilderBase::buildInstrNoInsert(unsigned Opcode) {
 
 MachineInstrBuilder MachineIRBuilderBase::insertInstr(MachineInstrBuilder MIB) {
   getMBB().insert(getInsertPt(), MIB);
-  if (State.InsertedInstr)
-    State.InsertedInstr(MIB);
+  recordInsertion(MIB);
   return MIB;
 }