Currently, the floating point instructions that depend on rounding mode are correctly marked in the PPC back end with an implicit use of the RM register. Similarly, instructions that explicitly define the register are marked with an implicit def of the same register. So for the most part, RM-using code won't be moved across RM-setting instructions.
However, calls are not marked as RM-setting instructions so code can be moved across calls. This is generally desired, but so is the ability to turn off this behaviour with an appropriate option - and -frounding-math really should be that option.
This patch provides a set of call instructions (for direct and indirect calls) that are marked with an implicit def of the RM register. These will be used for calls that are marked with the strictfp attribute.