Fix a bad overflow check pointed out by Ben.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185226 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/BlockFrequency.cpp b/lib/Support/BlockFrequency.cpp
index 8de517f..5e45e46 100644
--- a/lib/Support/BlockFrequency.cpp
+++ b/lib/Support/BlockFrequency.cpp
@@ -47,9 +47,7 @@
uint64_t x = W[1];
unsigned i;
- // This is really a 64-bit division.
- if (!x)
- return y / D;
+ assert(x != 0 && "This is really a 64-bit division");
// This long division algorithm automatically saturates on overflow.
for (i = 0; i < 64 && x; ++i) {
@@ -75,7 +73,7 @@
uint64_t MulRes = (MulHi << 32) + MulLo;
// If the product fits in 64 bits, just use built-in division.
- if (MulHi <= UINT32_MAX && MulRes <= MulLo) {
+ if (MulHi <= UINT32_MAX && MulRes >= MulLo) {
Frequency = MulRes / D;
return;
}
diff --git a/unittests/Support/BlockFrequencyTest.cpp b/unittests/Support/BlockFrequencyTest.cpp
index 4bcddfe..ca420fc 100644
--- a/unittests/Support/BlockFrequencyTest.cpp
+++ b/unittests/Support/BlockFrequencyTest.cpp
@@ -68,6 +68,11 @@
Freq = 0x1000000000000000ULL;
Freq /= BranchProbability(10000, 160000);
EXPECT_EQ(Freq.getFrequency(), UINT64_MAX);
+
+ // Try to cheat the multiplication overflow check.
+ Freq = 0x00000001f0000001ull;
+ Freq /= BranchProbability(1000, 0xf000000f);
+ EXPECT_EQ(33506781356485509ULL, Freq.getFrequency());
}
TEST(BlockFrequencyTest, ProbabilityCompare) {