On Fri, 19 Mar 2021, YunQiang Su wrote:
what about just rebuilding them ? They are broken, so why should we fix broken user binaries with kernel hacks ?
In fact without O32_FP64_SUPPORT option is enabled, the FP=0 mode is always used for FPXX.
As I noted in the discussion the choice of the FR mode for FPXX binaries is neutral performance-wise for R2 through R5, so as I previously stated it would be fine with me to use FR=0 rather than FR=1 for FPXX binaries with these architecture levels.
In fact it doesn't change the behaviour of kernel.
That is not true for R6. The use of the FRE mode with R6 does regress support for FPXX binaries performance-wise, which makes it unacceptable. And O32_FP64_SUPPORT is unconditionally selected for R6, so FR=0 (or FRE) is currently not used for FPXX with R6.
Maciej