[AArch64][GlobalISel] Make G_BLOCK_ADDR legal

[aemerson]

Summary

Make G_BLOCK_ADDR legal.

Instruction selection support will be coming in a subsequent patch.

lib/Target/AArch64/AArch64LegalizerInfo.cpp

getActionDefinitionsBuilder(
         {G_ATOMICRMW_XCHG, G_ATOMICRMW_ADD, G_ATOMICRMW_SUB, G_ATOMICRMW_AND,
          G_ATOMICRMW_OR, G_ATOMICRMW_XOR, G_ATOMICRMW_MIN, G_ATOMICRMW_MAX,
          G_ATOMICRMW_UMIN, G_ATOMICRMW_UMAX, G_ATOMIC_CMPXCHG})
         .legalIf(all(
             typeInSet(0, {s8, s16, s32, s64}), typeIs(1, p0),
             atomicOrderingAtLeastOrStrongerThan(0, AtomicOrdering::Monotonic)));
   }
 
+  getActionDefinitionsBuilder(G_BLOCK_ADDR).legalFor({p0});
+
   // Merge/Unmerge
   for (unsigned Op : {G_MERGE_VALUES, G_UNMERGE_VALUES}) {
     unsigned BigTyIdx = Op == G_MERGE_VALUES ? 0 : 1;
     unsigned LitTyIdx = Op == G_MERGE_VALUES ? 1 : 0;
 
     auto notValidElt = [](const LegalityQuery &Query, unsigned TypeIdx) {
       const LLT &Ty = Query.Types[TypeIdx];
       if (Ty.isVector()) {

test/CodeGen/AArch64/GlobalISel/legalize-blockaddress.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=aarch64-linux-gnu -O0 -run-pass=legalizer %s -o - | FileCheck %s
+--- |
+  target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+  target triple = "aarch64-none-linux-gnu"
+
+  @addr = global i8* null
+
+  define void @test_blockaddress() {
+    store i8* blockaddress(@test_blockaddress, %block), i8** @addr
+    indirectbr i8* blockaddress(@test_blockaddress, %block), [label %block]
+
+  block:                                            ; preds = %0
+    ret void
+  }
+
+...
+---
+name:            test_blockaddress
+alignment:       2
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: _ }
+  - { id: 1, class: _ }
+body:             |
+  ; CHECK-LABEL: name: test_blockaddress
+  ; CHECK: bb.0 (%ir-block.0):
+  ; CHECK:   successors: %bb.1(0x80000000)
+  ; CHECK:   [[BLOCK_ADDR:%[0-9]+]]:_(p0) = G_BLOCK_ADDR blockaddress(@test_blockaddress, %ir-block.block)
+  ; CHECK:   [[GV:%[0-9]+]]:_(p0) = G_GLOBAL_VALUE @addr
+  ; CHECK:   G_STORE [[BLOCK_ADDR]](p0), [[GV]](p0) :: (store 8 into @addr)
+  ; CHECK:   G_BRINDIRECT [[BLOCK_ADDR]](p0)
+  ; CHECK: bb.1.block (address-taken):
+  ; CHECK:   RET_ReallyLR
+  bb.1 (%ir-block.0):
+    %0:_(p0) = G_BLOCK_ADDR blockaddress(@test_blockaddress, %ir-block.block)
+    %1:_(p0) = G_GLOBAL_VALUE @addr
+    G_STORE %0(p0), %1(p0) :: (store 8 into @addr)
+    G_BRINDIRECT %0(p0)
+
+  bb.2.block (address-taken):
+    RET_ReallyLR
+
+...
+