[llvm-dev] GVN Hoist moving a store across load

[Krzysztof Parzyszek via llvm-dev]

Hi,

I have a scenario, roughly like this:

   if (...) {
     ... = *x
     *x = 0
   } else {
     ... = *x
     *x = 0
   }

The two sides are functionally different, but both load some value and 
then set it to 0.

After GVN Hoist, I get:

   *x = 0
   if (...) {
     ... = *x
   } else {
     ... = *x
   }

That is, the store was hoisted above the loads.

The code is not exactly public, so I can't just attach it as a testcase, 
but it seems like some simple check is missing somewhere.

Does this ring a bell?

-Krzysztof

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