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a64_emit_x64: EmitVAddrLookup: Use bzhi instruction when silently_mirror_page_table is active and BMI2 is available

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MerryMage 2020-06-21 14:32:48 +01:00
parent 809dfe9c54
commit b32fc5ab0f
1 changed files with 14 additions and 3 deletions
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17
src/backend/x64/a64_emit_x64.cpp
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@ -790,19 +790,30 @@ Xbyak::RegExp EmitVAddrLookup(BlockOfCode& code, A64EmitContext& ctx, size_t bit
EmitDetectMisaignedVAddr(code, ctx, bitsize, abort, vaddr, tmp);
code.mov(tmp, vaddr);
if (unused_top_bits == 0) {
code.mov(tmp, vaddr);
code.shr(tmp, int(page_bits));
} else if (ctx.conf.silently_mirror_page_table) {
if (valid_page_index_bits >= 32) {
code.shl(tmp, int(unused_top_bits));
code.shr(tmp, int(unused_top_bits + page_bits));
if (code.HasBMI2()) {
const Xbyak::Reg64 bit_count = ctx.reg_alloc.ScratchGpr();
code.mov(bit_count, unused_top_bits);
code.bzhi(tmp, vaddr, bit_count);
code.shr(tmp, int(page_bits));
ctx.reg_alloc.Release(bit_count);
} else {
code.mov(tmp, vaddr);
code.shl(tmp, int(unused_top_bits));
code.shr(tmp, int(unused_top_bits + page_bits));
}
} else {
code.mov(tmp, vaddr);
code.shr(tmp, int(page_bits));
code.and_(tmp, u32((1 << valid_page_index_bits) - 1));
}
} else {
ASSERT(valid_page_index_bits < 32);
code.mov(tmp, vaddr);
code.shr(tmp, int(page_bits));
code.test(tmp, u32(-(1 << valid_page_index_bits)));
code.jnz(abort, code.T_NEAR);