[InstCombine] Check for isa<Instruction> before using cast<>
Protects against casts from constexpr etc.
Reduced from oss-fuzz #4788 test case
llvm-svn: 321515
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 5e0778d..40e52ee 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2376,7 +2376,7 @@
// The compare intrinsic uses the above assumptions and therefore
// doesn't require additional flags.
if ((match(Arg0, m_OneUse(m_FSub(m_Value(A), m_Value(B)))) &&
- match(Arg1, m_Zero()) &&
+ match(Arg1, m_Zero()) && isa<Instruction>(Arg0) &&
cast<Instruction>(Arg0)->getFastMathFlags().noInfs())) {
if (Arg0IsZero)
std::swap(A, B);