gcc/ChangeLog:
PR rtl-optimization/20532
* simplify-rtx.c (simplify_binary_operation_1): Protect from
overflow when adding coefficients for PLUS or MINUS.
(simplify_binary_operation_1): Handle CONST_DOUBLE exact power of
two as multiplier.
gcc/testsuite/ChangeLog:
PR rtl-optimization/20532
* gcc.target/i386/badshift.c: New.

From-SVN: r96982