MSan workaround in Simulator::VisitBitfield.
This change shuffles the code in Simulator::VisitBitfield a bit to work around a MemorySanitizer bug. New code should not be any slower or less readable than before. More info: https://code.google.com/p/memory-sanitizer/issues/detail?id=50 R=jkummerow@chromium.org Review URL: https://codereview.chromium.org/212863002 Patch from Evgeniy Stepanov <eugenis@chromium.org>. git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20401 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
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@ -2108,8 +2108,9 @@ void Simulator::VisitBitfield(Instruction* instr) {
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// Rotate source bitfield into place.
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int64_t result = (static_cast<uint64_t>(src) >> R) | (src << (reg_size - R));
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// Determine the sign extension.
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int64_t topbits = ((1L << (reg_size - diff - 1)) - 1) << (diff + 1);
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int64_t signbits = extend && ((src >> S) & 1) ? topbits : 0;
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int64_t topbits_preshift = (1L << (reg_size - diff - 1)) - 1;
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int64_t signbits = (extend && ((src >> S) & 1) ? topbits_preshift : 0)
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<< (diff + 1);
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// Merge sign extension, dest/zero and bitfield.
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result = signbits | (result & mask) | (dst & ~mask);
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