[llvm] [InstCombine] Propagate ninf from fptrunc when folding `fptrunc fabs(X) -> fabs(fptrunc X)` (PR #143352)

[Nikita Popov via llvm-commits]

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@@ -1926,6 +1926,9 @@ Instruction *InstCombinerImpl::visitFPTrunc(FPTruncInst &FPT) {
       CallInst *NewCI =
           CallInst::Create(Overload, {InnerTrunc}, OpBundles, II->getName());
       NewCI->copyFastMathFlags(II);
+      // A normal value may be converted to an infinity.
+      if (II->getIntrinsicID() == Intrinsic::fabs)
+        NewCI->setHasNoInfs(FPT.hasNoInfs());
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nikic wrote:

Now that we have FMF on fptrunc, can we always use the fptrunc flags here instead and not bother with the intrinsic flags at all?

https://github.com/llvm/llvm-project/pull/143352