Odd behavior with native FMA instructions when first launching Julia

[musm]

I experienced weird response when it comes to FMA on Julia 1.4 .

First started Julia from the command line, without any flags (downloaded from julialang.org). Then I checked mulladd with code_native and find it's not using FMA CPU instructions and Base.Math.FMA_NATIVE also showed false... that was strange since as long as I've used julia this was always true and FMA always used native instruction.

Then I started Julia with -O3. Check thing again... muladd is correctly using native FMA, but Base.Math.FMA_NATIVE is false (makes sense since it's a precompile constant, but should be fixed regardless).

Then the strange behavior shows up. I then check julia again (without -O3 flag) and native FMA is working correctly in muladd (Base.Math.FMA_NATIVE still false).

[KristofferC]

FMA_NATIVE is broken: #33011.

[musm]

Thanks, updated issue to reflect the fact that when I first launched julia it was not using native FMA, but then ended up correctly using FMA after launching with -03.

[simonbyrne]

Closing as duplicate of #33011.