[AMDGPU][MC] Corrected error position for invalid operands

Generic parser may report an incorrect error position when an offending operand is followed by a comma.
See bug 48884 for details: https://bugs.llvm.org/show_bug.cgi?id=48884.

Differential Revision: https://reviews.llvm.org/D95674

Author: dpreobra

llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

@@ -4942,9 +4942,6 @@ bool AMDGPUAsmParser::ParseInstruction(ParseInstructionInfo &Info,
       Mode = OperandMode_NSA;
     OperandMatchResultTy Res = parseOperand(Operands, Name, Mode);
 
-    // Eat the comma or space if there is one.
-    trySkipToken(AsmToken::Comma);
-
     if (Res != MatchOperand_Success) {
       checkUnsupportedInstruction(Name, NameLoc);
       if (!Parser.hasPendingError()) {
@@ -4959,6 +4956,9 @@ bool AMDGPUAsmParser::ParseInstruction(ParseInstructionInfo &Info,
       }
       return true;
     }
+
+    // Eat the comma or space if there is one.
+    trySkipToken(AsmToken::Comma);
   }
 
   return false;

llvm/test/MC/AMDGPU/gfx10_err_pos.s

@@ -535,6 +535,11 @@ v_ceil_f16 v0, abs(neg(1))
 // CHECK-NEXT:{{^}}v_ceil_f16 v0, abs(neg(1))
 // CHECK-NEXT:{{^}}                   ^
 
+image_atomic_xor v4, v32, s[96:103] dmask:0x1 dim:, glc
+// CHECK: error: failed parsing operand.
+// CHECK-NEXT:{{^}}image_atomic_xor v4, v32, s[96:103] dmask:0x1 dim:, glc
+// CHECK-NEXT:{{^}}                                                  ^
+
 //==============================================================================
 // first register index should not exceed second index