[PATCH] D19178: Broaden FoldItoFPtoI to try and establish whether the integer value fits into the float type

[Eli Friedman via llvm-commits]

eli.friedman added inline comments.

================
Comment at: lib/Transforms/InstCombine/InstCombineCasts.cpp:1496
@@ +1495,3 @@
+                MostSignificantPossiblySetBit = std::max(HighestNotKnownZero,
+                                                         LowestNotKnownOne);
+            }
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If a value has unknown sign, isn't KnownZero.countLeadingOnes() always going to zero?

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Comment at: lib/Transforms/InstCombine/InstCombineCasts.cpp:1507
@@ +1506,3 @@
+    Safe = BitRange <= SignificandWidth && MostSignificantPossiblySetBit <
+      APFloat::semanticsMaxExponent(OpITy->getFltSemantics());
+  }
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Thinking about it a bit more, we don't actually care if the exponent overflows; the end result would be undef, so it doesn't matter.


https://reviews.llvm.org/D19178