pgsql: jit: Stop emitting some unnecessary instructions

jit: Stop emitting some unnecessary instructions

In EEOP_BOOL_AND_STEP* and EEOP_BOOL_OR_STEP*, we emitted pointlesss
store instructions to store to resnull/resvalue values that were just
loaded from the same fields in the previous instructions. They will
surely get optimized away by LLVM if any optimizations are enabled,
but it's better to not emit them in the first place. In
EEOP_BOOL_NOT_STEP, similar story with resnull.

In EEOP_NULLIF, when it returns NULL, there was also a redundant store
to resvalue just after storing a 0 to it. The value of resvalue
doesn't matter when resnull is set, so in fact even storing the 0 is
unnecessary, but I kept that because we tend to do that for general
tidiness.

Author: Xing Guo <higuoxing(at)gmail(dot)com>
Reviewed-by: Andreas Karlsson <andreas(at)proxel(dot)se>
Discussion: https://www.postgresql.org/message-id/CACpMh%2BC%3Dg13WdvzLRSponsVWGgxwDSMzQWM4Gz0heOyaA0-N6g@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/cfd7f36c83cdcf6322c7ea0d1d9ef62bc2b00375

Modified Files
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src/backend/jit/llvm/llvmjit_expr.c | 24 +++++++-----------------
1 file changed, 7 insertions(+), 17 deletions(-)