v8/test/cctest/test-diy-fp.cc

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#include <stdlib.h>

#include "src/base/numbers/diy-fp.h"
#include "src/base/platform/platform.h"
#include "src/init/v8.h"
#include "test/cctest/cctest.h"

namespace v8 {
namespace base {

TEST(Subtract) {
  DiyFp diy_fp1 = DiyFp(3, 0);
  DiyFp diy_fp2 = DiyFp(1, 0);
  DiyFp diff = DiyFp::Minus(diy_fp1, diy_fp2);

  CHECK_EQ(2, diff.f());
  CHECK_EQ(0, diff.e());
  diy_fp1.Subtract(diy_fp2);
  CHECK_EQ(2, diy_fp1.f());
  CHECK_EQ(0, diy_fp1.e());
}


TEST(Multiply) {
  DiyFp diy_fp1 = DiyFp(3, 0);
  DiyFp diy_fp2 = DiyFp(2, 0);
  DiyFp product = DiyFp::Times(diy_fp1, diy_fp2);

  CHECK_EQ(0, product.f());
  CHECK_EQ(64, product.e());
  diy_fp1.Multiply(diy_fp2);
  CHECK_EQ(0, diy_fp1.f());
  CHECK_EQ(64, diy_fp1.e());

  diy_fp1 = DiyFp(0x8000'0000'0000'0000, 11);
  diy_fp2 = DiyFp(2, 13);
  product = DiyFp::Times(diy_fp1, diy_fp2);
  CHECK_EQ(1, product.f());
  CHECK_EQ(11 + 13 + 64, product.e());

  // Test rounding.
  diy_fp1 = DiyFp(0x8000'0000'0000'0001, 11);
  diy_fp2 = DiyFp(1, 13);
  product = DiyFp::Times(diy_fp1, diy_fp2);
  CHECK_EQ(1, product.f());
  CHECK_EQ(11 + 13 + 64, product.e());

  diy_fp1 = DiyFp(0x7FFF'FFFF'FFFF'FFFF, 11);
  diy_fp2 = DiyFp(1, 13);
  product = DiyFp::Times(diy_fp1, diy_fp2);
  CHECK_EQ(0, product.f());
  CHECK_EQ(11 + 13 + 64, product.e());

  // Halfway cases are allowed to round either way. So don't check for it.

  // Big numbers.
  diy_fp1 = DiyFp(0xFFFF'FFFF'FFFF'FFFF, 11);
  diy_fp2 = DiyFp(0xFFFF'FFFF'FFFF'FFFF, 13);
  // 128bit result: 0xFFFFFFFFFFFFFFFE0000000000000001
  product = DiyFp::Times(diy_fp1, diy_fp2);
  CHECK_EQ(0xFFFF'FFFF'FFFF'FFFE, product.f());
  CHECK_EQ(11 + 13 + 64, product.e());
}

}  // namespace base
}  // namespace v8