[TableGen] Check for duplicate register tuple definitions. #95725
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Currently TableGen does not directly detect duplicate synthesized registers as can happen in this example:
def GPR128 : RegisterTuples<[sub0, sub1, sub2, sub3],
[(decimate (shl GPR32, 0), 1),
(decimate (shl GPR32, 1), 1),
(decimate (shl GPR32, 2), 1),
(decimate (shl GPR32, 3), 1)]>;
def GPR128_Aligned : RegisterTuples<[sub0, sub1, sub2, sub3],
[(decimate (shl GPR32, 0), 4),
(decimate (shl GPR32, 1), 4),
(decimate (shl GPR32, 2), 4),
(decimate (shl GPR32, 3), 4)]>;
TableGen does fail, but with an unrelated and difficult to understand error that happens downstream of tuple expansion:
"error: No SubRegIndex for R0_R1_R2_R3 in R0_R1_R2_R3".
This patch detects the problem directly during expansion and emits an error pointing the user to the actual issue:
"error: Register tuple redefines register 'R0_R1_R2_R3'".