[llvm] [AMDGPU] Fix MC/Disassembler/AMDGPU/decode-err.txt. (PR #96621)

[Ivan Kosarev via llvm-commits]

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@@ -1,17 +1,18 @@
-# RUN: llvm-mc -triple=amdgcn -mcpu=gfx900 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefix=GCN %s
-# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1100 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefixes=GFX11,W32 %s
-# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1100 -mattr=-WavefrontSize32,+WavefrontSize64 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefixes=GFX11,W64 %s
-# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1200 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefix=GFX12 %s
+# RUN: llvm-mc -triple=amdgcn -mcpu=gfx900 -disassemble -show-encoding -filetype=null < %s 2>&1 | FileCheck -check-prefix=GCN-ERR %s
+# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1100 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefixes=W32 %s
+# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1100 -mattr=-WavefrontSize32,+WavefrontSize64 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefixes=W64 %s
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kosarev wrote:

> The capitalized wavefrontsize features shouldn't even parse?

It seems to get lowered before processing. Not sure if it should or shouldn't be done, though.

Re negations: that would be an unrelated change anyway, so I will submit this as is, if no objections.

https://github.com/llvm/llvm-project/pull/96621