[llvm] [AMDGPU][GFX12] Support disassembling MUBUF instructions with arbitrary FORMAT values. (PR #95243)

[Matt Arsenault via llvm-commits]

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@@ -2447,7 +2447,13 @@ multiclass VBUFFER_MUBUF_Real_gfx12<bits<8> op, string real_name> {
   def _gfx12 : VBUFFER_Real_gfx12<op, ps, real_name> {
     // Set the last bit of format to 1 to avoid round-trip issues, as some tools
     // print BUF_FMT_INVALID for format 0.
-    let Inst{55} = 0b1;
+    let Inst{61-55} = 1;
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arsenm wrote:

I'm not sure how to read this. Is it setting the 6-bit value to 1, as in mostly zeroes? Given the comment, can we keep just setting bit 55 to 1 and then set the others to 0? 

https://github.com/llvm/llvm-project/pull/95243