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Commit 328aeb14 authored by verwaest@chromium.org's avatar verwaest@chromium.org
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Revert "Improved range analysis for bitwise operations." 

This reverts commit r15170

R=jkummerow@chromium.org

Review URL: https://chromiumcodereview.appspot.com/17093005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15173 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
parent 47ba2b2d
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Showing with 52 additions and 343 deletions
src/hydrogen-instructions.cc
View file @ 328aeb14
......@@ -289,8 +289,16 @@ static int32_t MulWithoutOverflow(int32_t a, int32_t b, bool* overflow) {
}
void Range::ToBitRange(BitRange* bits) const {
BitRange::SetFromRange(bits, lower_, upper_);
int32_t Range::Mask() const {
if (lower_ == upper_) return lower_;
if (lower_ >= 0) {
int32_t res = 1;
while (res < upper_) {
res = (res << 1) | 1;
}
return res;
}
return 0xffffffff;
}
......@@ -2374,38 +2382,50 @@ void HMathMinMax::InferRepresentation(HInferRepresentation* h_infer) {
Range* HBitwise::InferRange(Zone* zone) {
if (representation().IsInteger32()) {
BitRange left_bits, right_bits;
if (left()->HasRange()) {
left()->range()->ToBitRange(&left_bits);
if (op() == Token::BIT_XOR) {
if (left()->HasRange() && right()->HasRange()) {
// The maximum value has the high bit, and all bits below, set:
// (1 << high) - 1.
// If the range can be negative, the minimum int is a negative number with
// the high bit, and all bits below, unset:
// -(1 << high).
// If it cannot be negative, conservatively choose 0 as minimum int.
int64_t left_upper = left()->range()->upper();
int64_t left_lower = left()->range()->lower();
int64_t right_upper = right()->range()->upper();
int64_t right_lower = right()->range()->lower();
if (left_upper < 0) left_upper = ~left_upper;
if (left_lower < 0) left_lower = ~left_lower;
if (right_upper < 0) right_upper = ~right_upper;
if (right_lower < 0) right_lower = ~right_lower;
int high = MostSignificantBit(
static_cast<uint32_t>(
left_upper | left_lower | right_upper | right_lower));
int64_t limit = 1;
limit <<= high;
int32_t min = (left()->range()->CanBeNegative() ||
right()->range()->CanBeNegative())
? static_cast<int32_t>(-limit) : 0;
return new(zone) Range(min, static_cast<int32_t>(limit - 1));
}
if (right()->HasRange()) {
right()->range()->ToBitRange(&right_bits);
}
BitRange result;
switch (op()) {
case Token::BIT_AND:
result = BitRange::And(left_bits, right_bits);
break;
case Token::BIT_OR:
result = BitRange::Or(left_bits, right_bits);
break;
case Token::BIT_XOR:
result = BitRange::Xor(left_bits, right_bits);
break;
default:
UNREACHABLE();
}
int32_t lower = kMaxInt, upper = kMinInt; // 'empty' range.
result.ExtendRange(&lower, &upper);
return new(zone) Range(lower, upper);
} else {
return HValue::InferRange(zone);
}
const int32_t kDefaultMask = static_cast<int32_t>(0xffffffff);
int32_t left_mask = (left()->range() != NULL)
? left()->range()->Mask()
: kDefaultMask;
int32_t right_mask = (right()->range() != NULL)
? right()->range()->Mask()
: kDefaultMask;
int32_t result_mask = (op() == Token::BIT_AND)
? left_mask & right_mask
: left_mask | right_mask;
return (result_mask >= 0)
? new(zone) Range(0, result_mask)
: HValue::InferRange(zone);
}
......
src/hydrogen-instructions.h
View file @ 328aeb14
......@@ -43,7 +43,6 @@ namespace v8 {
namespace internal {
// Forward declarations.
class BitRange;
class HBasicBlock;
class HEnvironment;
class HInferRepresentation;
......@@ -260,7 +259,7 @@ class Range: public ZoneObject {
result->set_can_be_minus_zero(CanBeMinusZero());
return result;
}
void ToBitRange(BitRange* bits) const;
int32_t Mask() const;
void set_can_be_minus_zero(bool b) { can_be_minus_zero_ = b; }
bool CanBeMinusZero() const { return CanBeZero() && can_be_minus_zero_; }
bool CanBeZero() const { return upper_ >= 0 && lower_ <= 0; }
......@@ -307,60 +306,6 @@ class Range: public ZoneObject {
};
class BitRange {
public:
BitRange() : known_(0), bits_(0) { }
BitRange(int32_t known, int32_t bits)
: known_(known), bits_(bits & known) { }
static void SetFromRange(BitRange* bits, int32_t lower, int32_t upper) {
// Find a mask for the most significant bits that are the same for all
// values in the range.
int32_t same = ~(lower ^ upper);
// Flood zeros to any bits lower than the most significant zero.
same &= (same >> 1);
same &= (same >> 2);
same &= (same >> 4);
same &= (same >> 8);
same &= (same >> 16);
bits->known_ = same;
bits->bits_ = lower & same;
}
void ExtendRange(int32_t* lower, int32_t* upper) const {
int32_t limit1 = (~known_ & 0x80000000) | bits_;
int32_t limit2 = (~known_ & 0x7fffffff) | bits_;
*lower = Min(*lower, Min(limit1, limit2));
*upper = Max(*upper, Max(limit1, limit2));
}
static BitRange And(BitRange a, BitRange b) {
int32_t known = a.known_ & b.known_;
// Zeros in either operand become known.
known |= (a.known_ & ~a.bits_);
known |= (b.known_ & ~b.bits_);
return BitRange(known, a.bits_ & b.bits_);
}
static BitRange Or(BitRange a, BitRange b) {
int32_t known = a.known_ & b.known_;
// Ones in either operand become known.
known |= (a.known_ & a.bits_);
known |= (b.known_ & b.bits_);
return BitRange(known, a.bits_ | b.bits_);
}
static BitRange Xor(BitRange a, BitRange b) {
return BitRange(a.known_ & b.known_, a.bits_ ^ b.bits_);
}
private:
int32_t known_; // A mask of known bits.
int32_t bits_; // Values of known bits, zero elsewhere.
};
class UniqueValueId {
public:
UniqueValueId() : raw_address_(NULL) { }
......
test/cctest/cctest.gyp
View file @ 328aeb14
......@@ -52,7 +52,6 @@
'test-ast.cc',
'test-bignum.cc',
'test-bignum-dtoa.cc',
'test-bitrange.cc',
'test-circular-queue.cc',
'test-compare-nil-ic-stub.cc',
'test-compiler.cc',
......
test/cctest/test-bitrange.cc deleted 100644 → 0
View file @ 47ba2b2d
// Copyright 2013 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include <stdlib.h>
#include "v8.h"
#include "hydrogen-instructions.h"
#include "cctest.h"
using namespace v8::internal;
static int32_t GetLo(const BitRange& range) {
int32_t lo = kMaxInt, hi = kMinInt;
range.ExtendRange(&lo, &hi);
return lo;
}
static int32_t GetHi(const BitRange& range) {
int32_t lo = kMaxInt, hi = kMinInt;
range.ExtendRange(&lo, &hi);
return hi;
}
static void CheckOp(int32_t a_lo, int32_t a_hi,
int32_t b_lo, int32_t b_hi,
BitRange op(BitRange, BitRange),
int32_t expected_lo, int32_t expected_hi) {
BitRange a_range;
BitRange b_range;
BitRange::SetFromRange(&a_range, a_lo, a_hi);
BitRange::SetFromRange(&b_range, b_lo, b_hi);
BitRange result = op(a_range, b_range);
CHECK_EQ(expected_lo, GetLo(result));
CHECK_EQ(expected_hi, GetHi(result));
}
TEST(BitRangeConstants) {
// Converting a constant to BitRange and back is lossless.
for (int32_t i = -100; i <= 100; i++) {
BitRange r;
BitRange::SetFromRange(&r, i, i);
int32_t lo = kMaxInt, hi = kMinInt;
r.ExtendRange(&lo, &hi);
CHECK_EQ(i, lo);
CHECK_EQ(i, hi);
}
}
TEST(BitRangeConstantOps) {
for (int32_t a = -16; a <= 15; a++) {
for (int32_t b = -16; b <= 15; b++) {
CheckOp(a, a, b, b, &BitRange::And, a & b, a & b);
CheckOp(a, a, b, b, &BitRange::Or, a | b, a | b);
CheckOp(a, a, b, b, &BitRange::Xor, a ^ b, a ^ b);
}
}
}
static void CheckConvert(int32_t lo, int32_t hi,
int32_t expected_lo, int32_t expected_hi) {
BitRange range;
BitRange::SetFromRange(&range, lo, hi);
CHECK_EQ(expected_lo, GetLo(range));
CHECK_EQ(expected_hi, GetHi(range));
}
TEST(BitRangeConversion) {
// [0, 4] --> 000xxx
CheckConvert(0, 4, 0, 7);
CheckConvert(0, 5, 0, 7);
CheckConvert(0, 6, 0, 7);
CheckConvert(0, 7, 0, 7);
CheckConvert(1, 4, 0, 7);
CheckConvert(1, 5, 0, 7);
CheckConvert(1, 6, 0, 7);
CheckConvert(1, 7, 0, 7);
}
TEST(BitRangeConservativeApproximation) {
// Exhaustive test of 5-bit integers.
// The BitRange operation must always include all real possible values.
const int32_t kMin = -16;
const int32_t kMax = 15;
int count = 0;
int and_precise_count = 0;
int or_precise_count = 0;
int xor_precise_count = 0;
for (int32_t a_lo = kMin; a_lo <= kMax; a_lo++) {
for (int32_t a_hi = a_lo; a_hi <= kMax; a_hi++) {
for (int32_t b_lo = kMin; b_lo <= kMax; b_lo++) {
for (int32_t b_hi = a_lo; b_hi <= kMax; b_hi++) {
// Compute precise ranges.
int32_t and_lo = kMaxInt, and_hi = kMinInt;
int32_t or_lo = kMaxInt, or_hi = kMinInt;
int32_t xor_lo = kMaxInt, xor_hi = kMinInt;
for (int32_t a = a_lo; a <= a_hi; a++) {
for (int32_t b = b_lo; b <= b_hi; b++) {
int32_t a_and_b = a & b;
and_lo = Min(and_lo, a_and_b);
and_hi = Max(and_hi, a_and_b);
int32_t a_or_b = a | b;
or_lo = Min(or_lo, a_or_b);
or_hi = Max(or_hi, a_or_b);
int32_t a_xor_b = a ^ b;
xor_lo = Min(xor_lo, a_xor_b);
xor_hi = Max(xor_hi, a_xor_b);
}
}
BitRange a_range;
BitRange::SetFromRange(&a_range, a_lo, a_hi);
BitRange b_range;
BitRange::SetFromRange(&b_range, b_lo, b_hi);
++count;
// Precise range must always be included in approximate result.
BitRange and_range = BitRange::And(a_range, b_range);
CHECK(GetLo(and_range) <= and_lo);
CHECK(GetHi(and_range) >= and_hi);
if (GetLo(and_range) == and_lo && GetHi(and_range) == and_hi) {
++and_precise_count;
}
BitRange or_range = BitRange::Or(a_range, b_range);
CHECK(GetLo(or_range) <= or_lo);
CHECK(GetHi(or_range) >= or_hi);
if (GetLo(or_range) == or_lo && GetHi(or_range) == or_hi) {
++or_precise_count;
}
BitRange xor_range = BitRange::Xor(a_range, b_range);
CHECK(GetLo(xor_range) <= xor_lo);
CHECK(GetHi(xor_range) >= xor_hi);
if (GetLo(xor_range) == xor_lo && GetHi(xor_range) == xor_hi) {
++xor_precise_count;
}
}
}
}
}
CHECK_EQ(366080, count);
CHECK_EQ(35668, and_precise_count);
CHECK_EQ(35668, or_precise_count);
CHECK_EQ(37480, xor_precise_count);
}
TEST(BitRangeMultiRange) {
// Multiple ranges can be unioned with multiple calls to ExtendRange.
//
// HBitWise::InferRange is a 1x1 decomposition. Each input range is
// 'decomposed' into 1 BitRange. It is possible to do a more precise
// decompostion into several BitRanges. 2 BitRanges might be the sweet-spot
// since it prevents change-of-sign polluting the result.
//
// E.g. [-2,3] = {xxxxxxxx} as one BitRange, but is {1111111x, 000000xx} as
// two.
//
// [-2,3] ^ [-1,5] = {xxxxxxxx} ^ {xxxxxxxx} = xxxxxxxx
//
// With a 2x2 decomposition, there are 4 intermediate results.
//
// [-2,3] ^ [-1,5] = {1111111x, 000000xx} ^ {11111111, 00000xxx}
// result11 = 1111111x ^ 11111111 = 0000000x
// result12 = 1111111x ^ 00000xxx = 11111xxx
// result21 = 000000xx ^ 11111111 = 111111xx
// result22 = 000000xx ^ 00000xxx = 00000xxx
//
// These can be accumulated into a range as follows:
//
// result11.ExtendRange(&lower, &upper); // 0, 1
// result12.ExtendRange(&lower, &upper); // -8, 1
// result21.ExtendRange(&lower, &upper); // -8, 1
// result22.ExtendRange(&lower, &upper); // -8, 7
// = [-8,7]
{
BitRange r1(~0x000C, 0x0022); // 0010xx10
BitRange r2(~0x0003, 0x0004); // 0000x1xx
int32_t lo = kMaxInt, hi = kMinInt;
r1.ExtendRange(&lo, &hi);
CHECK_EQ(0x22, lo);
CHECK_EQ(0x2E, hi);
r2.ExtendRange(&lo, &hi);
CHECK_EQ(0x04, lo);
CHECK_EQ(0x2E, hi);
}
{
BitRange r1(~0, -1); // 11111111
BitRange r2(~1, 0); // 0000000x
int32_t lo = kMaxInt, hi = kMinInt;
r1.ExtendRange(&lo, &hi);
CHECK_EQ(-1, lo);
CHECK_EQ(-1, hi);
r2.ExtendRange(&lo, &hi);
CHECK_EQ(-1, lo);
CHECK_EQ(1, hi);
}
}
TEST(BitRangeOps) {
// xxxx & 000x => 000x
CheckOp(kMinInt, kMaxInt, 0, 1, &BitRange::And, 0, 1);
CheckOp(3, 7, 0, 0, &BitRange::Or, 0, 7);
CheckOp(4, 5, 0, 0, &BitRange::Or, 4, 5);
CheckOp(3, 7, 4, 4, &BitRange::Or, 4, 7);
CheckOp(0, 99, 4, 4, &BitRange::Or, 4, 127);
// 01xx ^ 0100 -> 00xx
CheckOp(4, 7, 4, 4, &BitRange::Xor, 0, 3);
// 00xx ^ 0100 -> 01xx
CheckOp(0, 3, 4, 4, &BitRange::Xor, 4, 7);
}
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