[TableGen] Check for duplicate register tuple definitions. (#95725)

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'".

0 files changed, 0 insertions, 0 deletions