[AMDGPU] Add new aliases ds_subrev_u32/u64 for ds_rsub_u32/u64 (#83118)

Note that the instructions have not been renamed and that there are no
corresponding aliases for ds_rsub_rtn_u32/u64. This matches SP3
behavior.

Author: jayfoad

llvm/lib/Target/AMDGPU/DSInstructions.td

@@ -1259,6 +1259,10 @@ defm DS_PK_ADD_RTN_F16    : DS_Real_gfx12<0x0aa>;
 defm DS_PK_ADD_BF16       : DS_Real_gfx12<0x09b>;
 defm DS_PK_ADD_RTN_BF16   : DS_Real_gfx12<0x0ab>;
 
+// New aliases added in GFX12 without renaming the instructions.
+def : MnemonicAlias<"ds_subrev_u32", "ds_rsub_u32">, Requires<[isGFX12Plus]>;
+def : MnemonicAlias<"ds_subrev_u64", "ds_rsub_u64">, Requires<[isGFX12Plus]>;
+
 //===----------------------------------------------------------------------===//
 // GFX11.
 //===----------------------------------------------------------------------===//

llvm/test/MC/AMDGPU/gfx12_asm_ds_alias.s

@@ -23,3 +23,9 @@ ds_min_rtn_f32 v5, v1, v2
 
 ds_min_rtn_f64 v[5:6], v1, v[2:3]
 // GFX12: [0x00,0x00,0xc8,0xd9,0x01,0x02,0x00,0x05]
+
+ds_subrev_u32 v1, v2
+// GFX12: ds_rsub_u32 v1, v2                      ; encoding: [0x00,0x00,0x08,0xd8,0x01,0x02,0x00,0x00]
+
+ds_subrev_u64 v1, v[2:3]
+// GFX12: ds_rsub_u64 v1, v[2:3]                  ; encoding: [0x00,0x00,0x08,0xd9,0x01,0x02,0x00,0x00]