LICM: use PatternMatch, IRBuilder in hoist BO assoc

Use PatternMatch when matching binary operators in hoistBOAssociation,
in order to make it easy to extend (this change is an NFC). Also use
IRBuilder when creating the new invariant instruction, so that the
constant-folder has an opportunity to constant-fold the new Instruction
that we desire to create (this change is not an NFC, and is a minor
improvement).

Author: artagnon

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -2841,15 +2841,18 @@ static bool hoistBOAssociation(Instruction &I, Loop &L,
   auto *Preheader = L.getLoopPreheader();
   assert(Preheader && "Loop is not in simplify form?");
 
-  auto *Inv = BinaryOperator::Create(Opcode, C1, C2, "invariant.op",
-                                     Preheader->getTerminator()->getIterator());
+  IRBuilder<> Builder(Preheader->getTerminator());
+  auto *Inv = Builder.CreateBinOp(Opcode, C1, C2, "invariant.op");
+
   auto *NewBO = BinaryOperator::Create(
       Opcode, LV, Inv, BO->getName() + ".reass", BO->getIterator());
 
   // Copy NUW for ADDs if both instructions have it.
   if (Opcode == Instruction::Add && BO->hasNoUnsignedWrap() &&
       BO0->hasNoUnsignedWrap()) {
-    Inv->setHasNoUnsignedWrap(true);
+    // If the constant-folder didn't kick in, and a new Instruction was created.
+    if (auto *I = dyn_cast<Instruction>(Inv))
+      I->setHasNoUnsignedWrap(true);
     NewBO->setHasNoUnsignedWrap(true);
   }
 

llvm/test/Transforms/LICM/sink-foldable.ll

@@ -77,7 +77,6 @@ return:
 define ptr @test2(i32 %j, ptr readonly %P, ptr readnone %Q) {
 ; CHECK-LABEL: @test2(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[INVARIANT_OP:%.*]] = add i32 1, 1
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.cond:
 ; CHECK-NEXT:    [[I_ADDR_0:%.*]] = phi i32 [ [[ADD_REASS:%.*]], [[IF_END:%.*]] ]
@@ -98,7 +97,7 @@ define ptr @test2(i32 %j, ptr readonly %P, ptr readnone %Q) {
 ; CHECK-NEXT:    [[ARRAYIDX2:%.*]] = getelementptr inbounds ptr, ptr [[ADD_PTR]], i64 [[IDX2_EXT]]
 ; CHECK-NEXT:    [[L1:%.*]] = load ptr, ptr [[ARRAYIDX2]], align 8
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp ugt ptr [[L1]], [[Q]]
-; CHECK-NEXT:    [[ADD_REASS]] = add i32 [[I_ADDR]], [[INVARIANT_OP]]
+; CHECK-NEXT:    [[ADD_REASS]] = add i32 [[I_ADDR]], 2
 ; CHECK-NEXT:    br i1 [[CMP2]], label [[LOOPEXIT2:%.*]], label [[FOR_COND]]
 ; CHECK:       loopexit0:
 ; CHECK-NEXT:    [[P0:%.*]] = phi ptr [ null, [[FOR_COND]] ]