hipe: bs_match_string bug fix #1234
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This fixes a HiPE bug reported on erlang-questions on 2/11/2016. The BEAM to ICode tranaslation of the bs_match_string instruction, written long ago for binaries (i.e., with byte-sized strings), tried to do a `clever' translation of even bit-sized strings using a HiPE primop that took a `Size' argument expressed in *bytes*. ICode is not really the place to do such a thing, and moreover there is really no reason for the HiPE primop not to take a Size argument expressed in *bits* instead. This commit changes the `Size' argument to be in bits, postpones the translation of the bs_match_string primop Fixed in a pair-programming/debugging session with @margnus1. until RTL and does a proper translation using bit-sized quantities there.
sverker
added
team:VM
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Put in testing for 19.2. @kostis Would you like to say something informative but not too long |
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Something like the following perhaps or is it too long? Fix native code compilation of binary pattern matching involving bitstring segments with explicit constants. The observed behavior was erroneous pattern matches. The bug only affects code containing constant-valued segments whose size is expressed in bits; it is triggered when the pattern matching against these segments fails (i.e., when the next clause needs to be tried). Such situations are quite rare, which probably explains why this bug managed to survive for many OTP releases; most likely from the first one that introduced bitstring (as opposed to binary) pattern matching. |
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Patch has passed first testings and has been assigned to be reviewed I am a script, I am not human |
This fixes a HiPE bug reported on erlang-questions on 2/11/2016.
The BEAM to ICode translation of the
bs_match_stringinstruction,written long ago for binaries (i.e., with byte-sized strings), tried
to do a clever translation of even bit-sized strings using a HiPE
primop that took a Size argument expressed in bytes.
ICode is not really the place to do such a thing, and moreover there
is really no reason for the HiPE primop not to take a Size argument
expressed in bits instead. This commit changes the Size argument
to be in bits, postpones the translation of the
bs_match_stringprimopuntil RTL and does a proper translation using bit-sized quantities there.
Fixed in a pair-programming/debugging session with @margnus1.