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Review request for Default, Ali Saidi, Gabe Black, Steve Reinhardt, and Nathan Binkert. Summary ------- X86: Don't read in dest regs if all bits are replaced. In x86, 32 and 64 bit writes to registers in when registers appear to be 32 or 64 bits wide overwrite all bits of the destination register. This change removes false dependencies in these cases where the previous value of a register doesn't need to be read to write a new value. New versions of most microops are created that have a "Big" suffix which simply overwrite their destination, and the right version to use is selected during microop allocation based on the selected data size. This does not change the performance of the O3 CPU model significantly, I assume because there are other false dependencies from the condition code bits in the flags register. Diffs ----- src/arch/isa_parser.py 4afd05b9485e src/arch/x86/isa/microops/ldstop.isa 4afd05b9485e src/arch/x86/isa/microops/limmop.isa 4afd05b9485e src/arch/x86/isa/microops/regop.isa 4afd05b9485e Diff: http://reviews.m5sim.org/r/464/diff Testing ------- Thanks, Gabe
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