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'".
edf5782f17