tree d1b7db6ffac38b7f6c0047d3f5d740153050b7ad
parent 9bdd9dc895ade41ec24f1a9918f70b23271ac89b
author Chengjun <chengjunp@Nvidia.com> 1744972205 -0700
committer GitHub <noreply@github.com> 1744972205 +0200
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[FlattenCFG] Fix an Imprecise Usage of AA (#128117)

In current `FlattenCFG`, using `isNoAlias` for two instructions is
imprecise. For example, when passing a store instruction and a load
instruction directly into `AA->isNoAlias`, it will always return
`NoAlias`. This happens because when checking the types of the two
Values, the store instruction (which has a `void` type) causes the
analysis to return `NoAlias`.

For instructions, we should use `getModRefInfo` instead of `isNoAlias`,
as aliasing is a concept of memory locations.

In this patch, `AAResults::getModRefInfo` is supported to take in two
instructions. It will check whether two instructions may access the same
memory location or not. And in `FlattenCFG`, we use this new helper
function to do the check instead of `isNoAlias`.

Unit tests and lit tests are also included to this patch.