Building on the initial work in 8187684, support for Math.multiplyHigh is implemented for the s390 and ppc platforms.

For [s390], work is limited to implementing an instruct for the MulHiL opcode in the s390.ad file.

For [ppc], there is no extra work required. The instruct for MulHiL already exists.

Microbenchmark performance:
s390: A speedup of 4x to 5x was observed across all available processor generations (z10, z196, z13).
ppc: A speedup of 10x to 15x was observed on Power8, slightly less on Power7.