[AArch64][GlobalISel] Fix legalizer crash trying to legalize <16 x i32> = G_BITCAST i512

Trying to do fewerElements on this results in an assert.

rdar://126373053
(cherry picked from commit eb3030a)

Author: aemerson

llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp

@@ -760,6 +760,9 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST)
       .legalForCartesianProduct({s32, v2s16, v4s8})
       .legalForCartesianProduct({s64, v8s8, v4s16, v2s32})
       .legalForCartesianProduct({s128, v16s8, v8s16, v4s32, v2s64, v2p0})
+      .lowerIf([=](const LegalityQuery &Query) {
+        return Query.Types[0].isVector() != Query.Types[1].isVector();
+      })
       .moreElementsToNextPow2(0)
       .clampNumElements(0, v8s8, v16s8)
       .clampNumElements(0, v4s16, v8s16)

llvm/test/CodeGen/AArch64/GlobalISel/legalize-bitcast.mir

@@ -0,0 +1,50 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 4
+# RUN: llc -mtriple=aarch64 -run-pass=legalizer -global-isel-abort=1  %s -o - | FileCheck %s
+---
+name:            scalar_to_oversize_vector
+tracksRegLiveness: true
+body:             |
+  ; CHECK-LABEL: name: scalar_to_oversize_vector
+  ; CHECK: bb.0:
+  ; CHECK-NEXT:   successors: %bb.1(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   G_BR %bb.1
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1:
+  ; CHECK-NEXT:   successors: %bb.1(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+  ; CHECK-NEXT:   [[UV:%[0-9]+]]:_(s32), [[UV1:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[C]](s64)
+  ; CHECK-NEXT:   [[UV2:%[0-9]+]]:_(s32), [[UV3:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[C]](s64)
+  ; CHECK-NEXT:   [[UV4:%[0-9]+]]:_(s32), [[UV5:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[C]](s64)
+  ; CHECK-NEXT:   [[UV6:%[0-9]+]]:_(s32), [[UV7:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[C]](s64)
+  ; CHECK-NEXT:   [[UV8:%[0-9]+]]:_(s32), [[UV9:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[C]](s64)
+  ; CHECK-NEXT:   [[UV10:%[0-9]+]]:_(s32), [[UV11:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[C]](s64)
+  ; CHECK-NEXT:   [[UV12:%[0-9]+]]:_(s32), [[UV13:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[C]](s64)
+  ; CHECK-NEXT:   [[UV14:%[0-9]+]]:_(s32), [[UV15:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[C]](s64)
+  ; CHECK-NEXT:   [[BUILD_VECTOR:%[0-9]+]]:_(<4 x s32>) = G_BUILD_VECTOR [[UV]](s32), [[UV1]](s32), [[UV2]](s32), [[UV3]](s32)
+  ; CHECK-NEXT:   [[BUILD_VECTOR1:%[0-9]+]]:_(<4 x s32>) = G_BUILD_VECTOR [[UV4]](s32), [[UV5]](s32), [[UV6]](s32), [[UV7]](s32)
+  ; CHECK-NEXT:   [[BUILD_VECTOR2:%[0-9]+]]:_(<4 x s32>) = G_BUILD_VECTOR [[UV8]](s32), [[UV9]](s32), [[UV10]](s32), [[UV11]](s32)
+  ; CHECK-NEXT:   [[BUILD_VECTOR3:%[0-9]+]]:_(<4 x s32>) = G_BUILD_VECTOR [[UV12]](s32), [[UV13]](s32), [[UV14]](s32), [[UV15]](s32)
+  ; CHECK-NEXT:   [[C1:%[0-9]+]]:_(p0) = G_CONSTANT i64 0
+  ; CHECK-NEXT:   G_STORE [[BUILD_VECTOR]](<4 x s32>), [[C1]](p0) :: (store (<4 x s32>), align 64)
+  ; CHECK-NEXT:   [[C2:%[0-9]+]]:_(p0) = G_CONSTANT i64 16
+  ; CHECK-NEXT:   G_STORE [[BUILD_VECTOR1]](<4 x s32>), [[C2]](p0) :: (store (<4 x s32>) into unknown-address + 16)
+  ; CHECK-NEXT:   [[C3:%[0-9]+]]:_(p0) = G_CONSTANT i64 32
+  ; CHECK-NEXT:   G_STORE [[BUILD_VECTOR2]](<4 x s32>), [[C3]](p0) :: (store (<4 x s32>) into unknown-address + 32, align 32)
+  ; CHECK-NEXT:   [[C4:%[0-9]+]]:_(p0) = G_CONSTANT i64 48
+  ; CHECK-NEXT:   G_STORE [[BUILD_VECTOR3]](<4 x s32>), [[C4]](p0) :: (store (<4 x s32>) into unknown-address + 48)
+  ; CHECK-NEXT:   G_BR %bb.1
+  bb.1:
+    %0:_(s512) = G_CONSTANT i512 0
+    %2:_(p0) = G_CONSTANT i64 0
+    G_BR %bb.2
+
+  bb.2:
+    %4:_(s512) = G_CONSTANT i512 0
+    %1:_(<16 x s32>) = G_BITCAST %4(s512)
+    %3:_(p0) = G_CONSTANT i64 0
+    G_STORE %1(<16 x s32>), %3(p0) :: (store (<16 x s32>))
+    G_BR %bb.2
+
+...