Fix implementation of instreth writes#1950
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aswaterman merged 2 commits intomasterfrom Apr 8, 2025
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No functional change intended; fixes implementation of a forthcoming bug fix.
Decrementing the counter in advance of incrementing it produces incorrect results when there's a carry-out. Fix by getting rid of this scheme altogher: just skip the increment if there was an expicit write.
jerryz123
approved these changes
Apr 8, 2025
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Thanks! I guess an official test and Spike agreeing is enough. |
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Decrementing the counter in advance of incrementing it produces incorrect results when there's a carry-out. Fix by getting rid of this scheme altogher: just skip the increment if there was an expicit write.
Looks like Spike tried to do the right thing here, but misimplemented it--i.e. it wasn't a misreading of the spec.
See test case riscv-software-src/riscv-tests@162d3e7 and ISA spec discussion riscv/riscv-isa-manual#1255
cc @Timmmm