[llvm] [IndVarSimplify] Ensure fp values can be represented as consecutive integers (PR #166649)

[Andrew Pinski via llvm-commits]

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@@ -265,6 +280,18 @@ bool IndVarSimplify::handleFloatingPointIV(Loop *L, PHINode *PN) {
       !ConvertToSInt(ExitValueVal->getValueAPF(), ExitValue))
     return false;
 
+  const auto &EVFltSema = ExitValueVal->getValueAPF().getSemantics();
+  if (!APFloat::isIEEELikeFP(EVFltSema))
+    return false;
+
+  uint64_t ExitValPrecision = APFloat::semanticsPrecision(EVFltSema);
+  if (ExitValPrecision >= 64)
+    return false;
+
+  uint64_t ExitValIntegerLimit = 1LL << ExitValPrecision;
+  if (uint64_t(std::abs(ExitValue)) > ExitValIntegerLimit)
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pinskia wrote:

Can ExitValue be INT64_MIN ?  If so then there would be undefined behavior here. I don't think it can be but it definitely deserves a comment.

https://github.com/llvm/llvm-project/pull/166649