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fdb04c6a86
Fixes #94120 and #94128. Pull Request resolved: https://github.com/pytorch/pytorch/pull/94900 Approved by: https://github.com/ezyang, https://github.com/jgong5
94 lines
2.3 KiB
C++
94 lines
2.3 KiB
C++
#pragma once
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#include <c10/macros/Macros.h>
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#include <c10/util/ArrayRef.h>
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#include <iterator>
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#include <numeric>
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#include <type_traits>
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// GCC has __builtin_mul_overflow from before it supported __has_builtin
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#ifdef _MSC_VER
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#define C10_HAS_BUILTIN_OVERFLOW() (0)
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#include <c10/util/llvmMathExtras.h>
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#include <intrin.h>
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#else
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#define C10_HAS_BUILTIN_OVERFLOW() (1)
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#endif
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namespace c10 {
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C10_ALWAYS_INLINE bool add_overflows(uint64_t a, uint64_t b, uint64_t* out) {
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#if C10_HAS_BUILTIN_OVERFLOW()
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return __builtin_add_overflow(a, b, out);
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#else
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unsigned long long tmp;
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#if defined(_M_IX86) || defined(_M_X64)
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auto carry = _addcarry_u64(0, a, b, &tmp);
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#else
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tmp = a + b;
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unsigned long long vector = (a & b) ^ ((a ^ b) & ~tmp);
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auto carry = vector >> 63;
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#endif
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*out = tmp;
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return carry;
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#endif
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}
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C10_ALWAYS_INLINE bool mul_overflows(uint64_t a, uint64_t b, uint64_t* out) {
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#if C10_HAS_BUILTIN_OVERFLOW()
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return __builtin_mul_overflow(a, b, out);
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#else
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*out = a * b;
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// This test isnt exact, but avoids doing integer division
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return (
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(c10::llvm::countLeadingZeros(a) + c10::llvm::countLeadingZeros(b)) < 64);
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#endif
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}
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C10_ALWAYS_INLINE bool mul_overflows(int64_t a, int64_t b, int64_t* out) {
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#if C10_HAS_BUILTIN_OVERFLOW()
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return __builtin_mul_overflow(a, b, out);
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#else
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volatile int64_t tmp = a * b;
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*out = tmp;
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if (a == 0 || b == 0) {
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return false;
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}
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return !(a == tmp / b);
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#endif
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}
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template <typename It>
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bool safe_multiplies_u64(It first, It last, uint64_t* out) {
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#if C10_HAS_BUILTIN_OVERFLOW()
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uint64_t prod = 1;
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bool overflow = false;
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for (; first != last; ++first) {
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overflow |= c10::mul_overflows(prod, *first, &prod);
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}
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*out = prod;
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return overflow;
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#else
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uint64_t prod = 1;
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uint64_t prod_log2 = 0;
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bool is_zero = false;
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for (; first != last; ++first) {
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auto x = static_cast<uint64_t>(*first);
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prod *= x;
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// log2(0) isn't valid, so need to track it specially
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is_zero |= (x == 0);
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prod_log2 += c10::llvm::Log2_64_Ceil(x);
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}
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*out = prod;
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// This test isnt exact, but avoids doing integer division
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return !is_zero && (prod_log2 >= 64);
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#endif
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}
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template <typename Container>
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bool safe_multiplies_u64(const Container& c, uint64_t* out) {
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return safe_multiplies_u64(c.begin(), c.end(), out);
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}
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} // namespace c10
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