[PATCH] [APFloat] Fix a bug in method 'fusedMultiplyAdd' (fixes PR20832).

Andrea Di Biagio Andrea_DiBiagio at sn.scee.net
Tue Sep 2 06:20:49 PDT 2014


When folding a fused multiply-add builtin call, make sure that we propagate the correct result in the case where the addend is zero, and the two other operands are finite non-zero.


define double @test() {
  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double 0.0)
  ret double %1

Before this patch, the instruction simplifier wrongly folded the builtin call in function @test to constant 'double 7.0'.
With this patch, method 'fusedMultiplyAdd' now correctly evaluates the multiply and returns the expected result (i.e. 56.0).

Added test fold-builtin-fma.ll with the reproducible from PR20832 plus extra test cases to verify the behavior of method 'fusedMultiplyAdd' in the presence of NaN/Inf operands.

Please let me know if ok to submit.

Andrea Di Biagio


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D5152.13161.patch
Type: text/x-patch
Size: 4173 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20140902/857bbd6f/attachment.bin>

More information about the llvm-commits mailing list