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Review request for Default and Gabe Black. Description ------- Changeset 9762:cfc4fa8529b3 --------------------------- x86: Add support for maintaining the x87 tag word The current implementation of the x87 never updates the x87 tag word. This is currently not a big issue since the simulated x87 never checks for stack overflows, however this becomes an issue when switching between a virtualized CPU and a simulated CPU. This changeset adds support, which is enabled by default, for updating the tag register to every floating point microop that updates the stack top using the spm mechanism. The new tag words is generated by the helper function X86ISA::genX87Tags(). This function is currently limited to flagging a stack position as valid or invalid and does not try to distinguish between the valid, zero, and special states. Diffs ----- src/arch/x86/faults.cc 9df73385c878 src/arch/x86/isa/microops/fpop.isa 9df73385c878 src/arch/x86/utility.hh 9df73385c878 src/arch/x86/utility.cc 9df73385c878 Diff: http://reviews.gem5.org/r/1915/diff/ Testing ------- Quick regressions pass. Tested with a handcoded assembly program that pushes and pops things on the x87 stack. Solves a SIGFPE problem when switching between simulated and virtualized CPUs (the FTW bits are used to determine if there is a stack overflow/underflow). Thanks, Andreas Sandberg _______________________________________________ gem5-dev mailing list [email protected] http://m5sim.org/mailman/listinfo/gem5-dev
