[llvm] [AMDGPU][MC] Add GFX12 SMEM encoding (PR #75215)

[Piotr Sobczak via llvm-commits]

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@@ -1235,28 +1239,79 @@ defm S_ATC_PROBE_BUFFER : SM_Real_Probe_gfx11 <0x23>;
 // GFX12.
 //===----------------------------------------------------------------------===//
 
-class SMEM_Real_gfx12<bits<8> op, SM_Pseudo ps, string opName = ps.Mnemonic> :
-    SMEM_Real_10Plus_common<op, ps, opName, SIEncodingFamily.GFX12,
+class SMEM_Real_gfx12Plus<bits<6> op, SM_Pseudo ps, string opName,
+                          int subtarget, RegisterWithSubRegs sgpr_null> :
+    SM_Real<ps, opName>, SIMCInstr<ps.PseudoInstr, subtarget>, Enc64 {
+
+  let Inst{18-13} = op;
+  let Inst{31-26} = 0x3d;
+
+  let Inst{55-32} = !if(ps.has_offset, offset{23-0}, !if(ps.has_soffset, 0, ?));
+  let Inst{63-57} = !if(ps.has_soffset, soffset{6-0},
+                        !if(ps.has_offset, sgpr_null.HWEncoding{6-0}, ?));
+}
+
+class SMEM_Real_gfx12<bits<6> op, SM_Pseudo ps, string opName = ps.Mnemonic> :
+    SMEM_Real_gfx12Plus<op, ps, opName, SIEncodingFamily.GFX12,
                             SGPR_NULL_gfx11plus> {
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piotrAMD wrote:

Nit: indentation (align `SGPR_NULL_gfx11plus` with `op`).

https://github.com/llvm/llvm-project/pull/75215