Odd error message when compiling Ada xref

[Richard Kenner]

../../xgcc -c -I./ -I../rts -I. -I/gcc/gcc/gcc-head/gcc/ada -B../../ -O2 -g -O2 -gnatpg -gnata -I- /gcc/gcc/gcc-head/gcc/ada/xr_tabls.adb
/gcc/gcc/gcc-head/gcc/ada/xr_tabls.adb: In function `Xr_Tabls.Get_References':
/gcc/gcc/gcc-head/gcc/ada/xr_tabls.adb:1579: error: Definition in block 8 does not dominate use in block 7
for SSA_NAME: arr<D5689>_4
in statement:
#   arr<D5689>_100 = V_MAY_DEF <arr<D5689>_4>;
arr<D5689>.P_BOUNDS<D569> = arr$P_BOUNDS<D10039>_8;