[ARM] GlobalISel: Support SP in regbankselect

We used to hit an unreachable in getRegBankFromRegClass when dealing with the
stack pointer. This commit adds support for the GPRsp reg class.

llvm-svn: 297621

llvm/lib/Target/ARM/ARMRegisterBankInfo.cpp

@@ -180,6 +180,7 @@ const RegisterBank &ARMRegisterBankInfo::getRegBankFromRegClass(
   switch (RC.getID()) {
   case GPRRegClassID:
   case GPRnopcRegClassID:
+  case GPRspRegClassID:
   case tGPR_and_tcGPRRegClassID:
   case tGPRRegClassID:
     return getRegBank(ARM::GPRRegBankID);

llvm/test/CodeGen/ARM/GlobalISel/arm-regbankselect.mir

@@ -8,6 +8,8 @@
   define void @test_loads() #0 { ret void }
   define void @test_stores() #0 { ret void }
 
+  define void @test_stack() { ret void }
+
   define void @test_gep() { ret void }
 
   define void @test_constants() { ret void }
@@ -200,6 +202,39 @@ body:             |
     G_STORE %6(s64), %0 :: (store 8)
     BX_RET 14, _, implicit %r0
 
+...
+---
+name:            test_stack
+# CHECK-LABEL: name: test_stack
+legalized:       true
+regBankSelected: false
+selected:        false
+# CHECK: registers:
+# CHECK: - { id: 0, class: gprb }
+# CHECK: - { id: 1, class: gprb }
+# CHECK: - { id: 2, class: gprb }
+# CHECK: - { id: 3, class: gprb }
+# CHECK: - { id: 4, class: gprb }
+registers:
+  - { id: 0, class: _ }
+  - { id: 1, class: _ }
+  - { id: 2, class: _ }
+  - { id: 3, class: _ }
+  - { id: 4, class: _ }
+fixedStack:
+  - { id: 0, offset: 0, size: 4, alignment: 4, isImmutable: true, isAliased: false }
+body:             |
+  bb.0:
+    %0(p0) = G_FRAME_INDEX %fixed-stack.0
+    %1(s32) = G_LOAD %0(p0) :: (load 4 from %fixed-stack.0, align 0)
+
+    %2(p0) = COPY %sp
+    %3(s32) = G_CONSTANT i32 8
+    %4(p0) = G_GEP %2, %3(s32)
+    G_STORE %1(s32), %4(p0) :: (store 4)
+
+    BX_RET 14, _
+
 ...
 ---
 name:            test_gep