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Avoid unnecessary stores in readVarint on AArch64 #677

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Avoid unnecessary stores in readVarint on AArch64 #677

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54 changes: 35 additions & 19 deletions thrift/lib/cpp/util/VarintUtils-inl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -139,43 +139,59 @@ size_t readVarintMediumSlowUnrolledX86(T& value, const uint8_t* p) {
template <class T>
size_t readVarintMediumSlowUnrolledAarch64(T& result, const uint8_t* p) {
// clang-format off
T tmp_result = 0;
T byte;
byte = *p++; result = (byte & 0x7f);
if (UNLIKELY(!(byte & 0x80)))
byte = *p++; tmp_result = (byte & 0x7f);
if (UNLIKELY(!(byte & 0x80))) {
result = tmp_result;
return 1;
byte = *p++; result |= (byte & 0x7f) << 7;
}
byte = *p++; tmp_result |= (byte & 0x7f) << 7;
if constexpr (sizeof(T) == 1) {
if (UNLIKELY((byte & 0x80)))
if (UNLIKELY((byte & 0x80)))
throwInvalidVarint();
result = tmp_result;
return 2;
} else {
if (UNLIKELY(!(byte & 0x80)))
if (UNLIKELY(!(byte & 0x80))){
result = tmp_result;
return 2;
byte = *p++; result |= (byte & 0x7f) << 14;
}
byte = *p++; tmp_result |= (byte & 0x7f) << 14;
if constexpr (sizeof(T) == 2) {
if (UNLIKELY((byte & 0x80)))
if (UNLIKELY((byte & 0x80)))
throwInvalidVarint();
result = tmp_result;
return 3;
} else {
if (UNLIKELY(!(byte & 0x80)))
if (UNLIKELY(!(byte & 0x80))){
result = tmp_result;
return 3;
byte = *p++; result |= (byte & 0x7f) << 21;
if (UNLIKELY(!(byte & 0x80)))
}
byte = *p++; tmp_result |= (byte & 0x7f) << 21;
if (UNLIKELY(!(byte & 0x80))) {
result = tmp_result;
return 4;
byte = *p++; result |= (byte & 0x7f) << 28;
}
byte = *p++; tmp_result |= (byte & 0x7f) << 28;
if constexpr (sizeof(T) == 4) {
if (UNLIKELY((byte & 0x80)))
if (UNLIKELY((byte & 0x80)))
throwInvalidVarint();
result = tmp_result;
return 5;
} else {
if (UNLIKELY(!(byte & 0x80))) return 5;
byte = *p++; result |= (byte & 0x7f) << 35; if (UNLIKELY(!(byte & 0x80))) return 6;
byte = *p++; result |= (byte & 0x7f) << 42; if (UNLIKELY(!(byte & 0x80))) return 7;
byte = *p++; result |= (byte & 0x7f) << 49; if (UNLIKELY(!(byte & 0x80))) return 8;
byte = *p++; result |= (byte & 0x7f) << 56; if (UNLIKELY(!(byte & 0x80))) return 9;
byte = *p; result |= (byte & 0x7f) << 63;
if (UNLIKELY((byte & 0x80)))
if (UNLIKELY(!(byte & 0x80))) {
result = tmp_result;
return 5;
}
byte = *p++; tmp_result |= (byte & 0x7f) << 35; if (UNLIKELY(!(byte & 0x80))) { result = tmp_result; return 6; }
byte = *p++; tmp_result |= (byte & 0x7f) << 42; if (UNLIKELY(!(byte & 0x80))) { result = tmp_result; return 7; }
byte = *p++; tmp_result |= (byte & 0x7f) << 49; if (UNLIKELY(!(byte & 0x80))) { result = tmp_result; return 8; }
byte = *p++; tmp_result |= (byte & 0x7f) << 56; if (UNLIKELY(!(byte & 0x80))) { result = tmp_result; return 9; }
byte = *p; tmp_result |= (byte & 0x7f) << 63;
if (UNLIKELY((byte & 0x80)))
throwInvalidVarint();
result = tmp_result;
return 10;
}
}
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