reinstate r222872: Peephole optimization in switch table lookup: reuse the guarding table comparison if possible.
Fixed missing dominance check.
Original commit message:
This optimization tries to reuse the generated compare instruction, if there is a comparison against the default value after the switch.
Example:
if (idx < tablesize)
r = table[idx]; // table does not contain default_value
else
r = default_value;
if (r != default_value)
...
Is optimized to:
cond = idx < tablesize;
if (cond)
r = table[idx];
else
r = default_value;
if (cond)
...
Jump threading will then eliminate the second if(cond).
llvm-svn: 222891
2 files changed