Request for reviews (S): 7063674: Wrong results from basic comparisons after calls to Long.bitCount(long)
christian.thalinger at oracle.com
Mon Jun 11 16:22:10 PDT 2012
On Jun 11, 2012, at 4:14 PM, Vladimir Kozlov wrote:
> I looked around and ReverseBytes instructions (which use shifts in addition to bswap) also missing KILL cr.
Good catch. I fixed them too and updated the webrev.
> Christian Thalinger wrote:
>> 7063674: Wrong results from basic comparisons after calls to Long.bitCount(long)
>> We are scheduling popcnt instructions between compare and branch/conditional
>> move instructions because AD instructs are not defined to kill flags.
>> But the Intel Instruction Set Reference says for POPCNT:
>> Flags Affected
>> OF, SF, ZF, AF, CF, PF are all cleared. ZF is set if SRC = 0, otherwise ZF is cleared
>> The fix is to kill the flags in instructs that are using popcnt instructions.
>> Tested with test case of CR. src/cpu/x86/vm/x86_32.ad
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