[AMDGPU] Remove s_subvector_loop_begin/end for GFX12 (#74451)

Author: jayfoad

llvm/lib/Target/AMDGPU/SOPInstructions.td

@@ -1100,10 +1100,14 @@ let SubtargetPredicate = isGFX10Plus in {
       "$simm16"> {
     let has_sdst = 0;
   }
+} // End SubtargetPredicate = isGFX10Plus
 
+let SubtargetPredicate = isGFX10GFX11 in {
   def S_SUBVECTOR_LOOP_BEGIN : SOPK_32_BR<"s_subvector_loop_begin">;
   def S_SUBVECTOR_LOOP_END   : SOPK_32_BR<"s_subvector_loop_end">;
+} // End SubtargetPredicate = isGFX10GFX11
 
+let SubtargetPredicate = isGFX10Plus in {
   def S_WAITCNT_VSCNT   : SOPK_WAITCNT<"s_waitcnt_vscnt">;
   def S_WAITCNT_VMCNT   : SOPK_WAITCNT<"s_waitcnt_vmcnt">;
   def S_WAITCNT_EXPCNT  : SOPK_WAITCNT<"s_waitcnt_expcnt">;

llvm/test/MC/AMDGPU/gfx12_unsupported.s

@@ -0,0 +1,11 @@
+// RUN: not llvm-mc -arch=amdgcn -mcpu=gfx1200 %s 2>&1 | FileCheck --implicit-check-not=error: %s
+
+//===----------------------------------------------------------------------===//
+// Unsupported instructions.
+//===----------------------------------------------------------------------===//
+
+s_subvector_loop_begin s0, 0x1234
+// CHECK: :[[@LINE-1]]:{{[0-9]+}}: error: instruction not supported on this GPU
+
+s_subvector_loop_end s0, 0x1234
+// CHECK: :[[@LINE-1]]:{{[0-9]+}}: error: instruction not supported on this GPU