Request for reviews (S): 7063674: Wrong results from basic comparisons after calls to Long.bitCount(long) (original) (raw)

Christian Thalinger christian.thalinger at oracle.com
Mon Jun 11 15:35:53 PDT 2012

http://cr.openjdk.java.net/~twisti/7063674

7063674: Wrong results from basic comparisons after calls to Long.bitCount(long) Reviewed-by:

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 src/cpu/x86/vm/x86_64.ad

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