[AArch64][SME] Fix frame lowering not using a base pointer for SME functions. (#91643)

The existing code is checking for the presence of the +sve subtarget
feature
when deciding to use a base pointer for the function, but this check
doesn't
work when only +sme is used.

rdar://126878490

Author: aemerson

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

@@ -552,7 +552,8 @@ bool AArch64RegisterInfo::hasBasePointer(const MachineFunction &MF) const {
     if (hasStackRealignment(MF))
       return true;
 
-    if (MF.getSubtarget<AArch64Subtarget>().hasSVE()) {
+    auto &ST = MF.getSubtarget<AArch64Subtarget>();
+    if (ST.hasSVE() || ST.isStreaming()) {
       const AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
       // Frames that have variable sized objects and scalable SVE objects,
       // should always use a basepointer.

llvm/test/CodeGen/AArch64/framelayout-sve-basepointer.mir

@@ -1,4 +1,11 @@
-# RUN: llc -mtriple=aarch64-none-linux-gnu -run-pass=prologepilog -mattr=+sve %s -o - | FileCheck %s
+# RUN: llc -mtriple=aarch64-none-linux-gnu -run-pass=prologepilog %s -o - | FileCheck %s
+--- |
+    define void @hasBasepointer() #0 { ret void }
+    define void @hasBasepointer_sme_streaming() #1 { ret void }
+
+    attributes #0 = { "target-features"="+sve" }
+    attributes #1 = { "target-features"="+sme" "aarch64_pstate_sm_enabled" }
+...
 ---
 # This test verifies that the basepointer is available in presence of SVE stack objects.
 name: hasBasepointer
@@ -21,3 +28,25 @@ body: |
     STRXui $x0, %stack.1, 0
     RET_ReallyLR
 ...
+---
+# Likewise with only SME with a streaming function.
+name: hasBasepointer_sme_streaming
+# CHECK-LABEL: name: hasBasepointer_sme_streaming
+# CHECK: bb.0:
+# CHECK:      $sp = frame-setup SUBXri $sp, 16, 0
+# CHECK-NEXT: $sp = frame-setup ADDVL_XXI $sp, -1
+# CHECK-NEXT: $x19 = ADDXri $sp, 0, 0
+# CHECK:      STRXui $x0, $x19, 0
+tracksRegLiveness: true
+frameInfo:
+  isFrameAddressTaken: true
+stack:
+  - { id: 0, type: variable-sized,  alignment: 1 }
+  - { id: 1, name: '', size: 16, alignment: 8 }
+  - { id: 2, stack-id: scalable-vector, size: 16, alignment: 16 }
+body: |
+  bb.0:
+    liveins: $x0
+    STRXui $x0, %stack.1, 0
+    RET_ReallyLR
+...