[llvm] [AMDGPU][MC] Improve error message for missing dim operand (PR #96588)

[Matt Arsenault via llvm-commits]

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@@ -4006,6 +4007,29 @@ bool AMDGPUAsmParser::validateMIMGGatherDMask(const MCInst &Inst) {
   return DMask == 0x1 || DMask == 0x2 || DMask == 0x4 || DMask == 0x8;
 }
 
+bool AMDGPUAsmParser::validateMIMGDim(const MCInst &Inst,
+                                      const OperandVector &Operands) {
+  if (!isGFX10Plus())
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arsenm wrote:

can this be a named feature instead of a generation check 

https://github.com/llvm/llvm-project/pull/96588