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[bigint] Set max BigInt size to 1M bits

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We can bump it up later if there is need.

Taking digit size into account for the max length in digits
makes the max length in bits consistent across architectures.

Bug: v8:6791
Change-Id: Id5205d2d308bbe6a38f8ff1ee19c082bedbeb74a
Reviewed-on: https://chromium-review.googlesource.com/717176
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48514}
This commit is contained in:
Jakob Kummerow 2017-10-12 14:00:27 -07:00 committed by Commit Bot
parent e770879eee
commit ae32e6e121
1 changed files with 6 additions and 2 deletions
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8
src/objects/bigint.h
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@ -70,8 +70,8 @@ class BigInt : public HeapObject {
// The maximum length that the current implementation supports would be
// kMaxInt / kDigitBits. However, we use a lower limit for now, because
// raising it later is easier than lowering it.
static const int kMaxLengthBits = 20;
static const int kMaxLength = (1 << kMaxLengthBits) - 1;
// Support up to 1 million bits.
static const int kMaxLength = 1024 * 1024 / (kPointerSize * kBitsPerByte);
class BodyDescriptor;
@ -84,6 +84,8 @@ class BigInt : public HeapObject {
static const int kDigitBits = kDigitSize * kBitsPerByte;
static const int kHalfDigitBits = kDigitBits / 2;
static const digit_t kHalfDigitMask = (1ull << kHalfDigitBits) - 1;
// kMaxLength definition assumes this:
STATIC_ASSERT(kDigitSize == kPointerSize);
// Private helpers for public methods.
static Handle<BigInt> Copy(Handle<BigInt> source);
@ -164,6 +166,8 @@ class BigInt : public HeapObject {
return static_cast<digit_t>(~x) == 0;
}
static const int kMaxLengthBits = 20;
STATIC_ASSERT(kMaxLength <= ((1 << kMaxLengthBits) - 1));
class LengthBits : public BitField<int, 0, kMaxLengthBits> {};
class SignBits : public BitField<bool, LengthBits::kNext, 1> {};