Fix a bad overflow check pointed out by Ben.
llvm-svn: 185226
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@ -47,9 +47,7 @@ static uint64_t div96bit(uint64_t W[2], uint32_t D) {
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uint64_t x = W[1];
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unsigned i;
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// This is really a 64-bit division.
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if (!x)
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return y / D;
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assert(x != 0 && "This is really a 64-bit division");
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// This long division algorithm automatically saturates on overflow.
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for (i = 0; i < 64 && x; ++i) {
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@ -75,7 +73,7 @@ void BlockFrequency::scale(uint32_t N, uint32_t D) {
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uint64_t MulRes = (MulHi << 32) + MulLo;
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// If the product fits in 64 bits, just use built-in division.
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if (MulHi <= UINT32_MAX && MulRes <= MulLo) {
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if (MulHi <= UINT32_MAX && MulRes >= MulLo) {
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Frequency = MulRes / D;
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return;
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}
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@ -68,6 +68,11 @@ TEST(BlockFrequencyTest, Saturate) {
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Freq = 0x1000000000000000ULL;
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Freq /= BranchProbability(10000, 160000);
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EXPECT_EQ(Freq.getFrequency(), UINT64_MAX);
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// Try to cheat the multiplication overflow check.
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Freq = 0x00000001f0000001ull;
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Freq /= BranchProbability(1000, 0xf000000f);
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EXPECT_EQ(33506781356485509ULL, Freq.getFrequency());
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}
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TEST(BlockFrequencyTest, ProbabilityCompare) {
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