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optimizer: do not delete statements that may not :terminate #52999

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merged 3 commits into from
Apr 15, 2024
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Fixes #52991.
Currently this commit marks the test case added in #52954 as broken since it has relied on the behavior of #52991.
I'm planning to add followup changes in a separate commit.

@aviatesk aviatesk force-pushed the avi/optimization-flags-refactor branch from 2345411 to 65c7d1d Compare January 22, 2024 05:03
Base automatically changed from avi/optimization-flags-refactor to master January 22, 2024 09:46
@aviatesk aviatesk force-pushed the avi/52991 branch 2 times, most recently from 10dc95b to 0b1bda6 Compare January 23, 2024 11:33
@oscardssmith oscardssmith added bugfix This change fixes an existing bug compiler:optimizer Optimization passes (mostly in base/compiler/ssair/) labels Jan 23, 2024
@Keno Keno removed the bugfix This change fixes an existing bug label Jan 24, 2024
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Keno commented Jan 24, 2024

Not a bugfix. This is an implementation of the #40009 decision.

@aviatesk aviatesk added the triage This should be discussed on a triage call label Jan 24, 2024
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Added the triage label instead.

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Keno commented Jan 24, 2024

Should add the test cases from #40009

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From triage: Nobody supports keeping this UB. Go for it!

@LilithHafner LilithHafner removed the triage This should be discussed on a triage call label Mar 28, 2024
@aviatesk aviatesk added the merge me PR is reviewed. Merge when all tests are passing label Apr 15, 2024
@aviatesk aviatesk merged commit 98f4747 into master Apr 15, 2024
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@aviatesk aviatesk removed the merge me PR is reviewed. Merge when all tests are passing label Apr 15, 2024
aviatesk added a commit that referenced this pull request Jun 5, 2024
#54323 ensures that all frames within a cycle have the
same, cycle valid effects. However, `src.ssaflags` is calculated using
partial effects, so when the effects of a `frame` within the cycle are
updated, there would be an inconsistency between `frame.ipo_effects` and
`frame.src.ssaflags`. Due to this inconsistency, #54323
breaks the test cases from #51092, when backported to
v1.11. On the surface this is because #52999 hasn't been
backported to v1.11, but the fundamental issue lies in this
inconsistency between cycle effects and `ssaflags`.

This commit uses a somewhat hacky approach to resolve this. It
identifies statements involved in the cycle comparing `stmt_edges` to
`callers_in_cycle`, and updates `ssaflags` according to new cycle valid
effects if necessary. This resolves the issue, but ideally, it should be
implemented more safely with the new `edges` format that will be
implemented in the future. For now, this approach should be okay.
aviatesk added a commit that referenced this pull request Jun 6, 2024
#54323 ensures that all frames within a cycle have the
same, cycle valid effects. However, `src.ssaflags` is calculated using
partial effects, so when the effects of a `frame` within the cycle are
updated, there would be an inconsistency between `frame.ipo_effects` and
`frame.src.ssaflags`. Due to this inconsistency, #54323
breaks the test cases from #51092, when backported to
v1.11. On the surface this is because #52999 hasn't been
backported to v1.11, but the fundamental issue lies in this
inconsistency between cycle effects and `ssaflags`.

This commit uses a somewhat hacky approach to resolve this. It
identifies statements involved in the cycle comparing `stmt_edges` to
`callers_in_cycle`, and updates `ssaflags` according to new cycle valid
effects if necessary. This resolves the issue, but ideally, it should be
implemented more safely with the new `edges` format that will be
implemented in the future. For now, this approach should be okay.
aviatesk added a commit that referenced this pull request Jun 6, 2024
#54323 ensures that all frames within a cycle have the
same, cycle valid effects. However, `src.ssaflags` is calculated using
partial effects, so when the effects of a `frame` within the cycle are
updated, there would be an inconsistency between `frame.ipo_effects` and
`frame.src.ssaflags`. Due to this inconsistency, #54323
breaks the test cases from #51092, when backported to
v1.11. On the surface this is because #52999 hasn't been
backported to v1.11, but the fundamental issue lies in this
inconsistency between cycle effects and `ssaflags`.

This commit uses a somewhat hacky approach to resolve this. It
identifies statements involved in the cycle comparing `stmt_edges` to
`callers_in_cycle`, and updates `ssaflags` according to new cycle valid
effects if necessary. This resolves the issue, but ideally, it should be
implemented more safely with the new `edges` format that will be
implemented in the future. For now, this approach should be okay.
aviatesk added a commit that referenced this pull request Jun 6, 2024
#54323 ensures that all frames within a cycle have the
same, cycle valid effects. However, `src.ssaflags` is calculated using
partial effects, so when the effects of a `frame` within the cycle are
updated, there would be an inconsistency between `frame.ipo_effects` and
`frame.src.ssaflags`. Due to this inconsistency, #54323
breaks the test cases from #51092, when backported to
v1.11. On the surface this is because #52999 hasn't been
backported to v1.11, but the fundamental issue lies in this
inconsistency between cycle effects and `ssaflags`.

This commit uses a somewhat hacky approach to resolve this. It
identifies statements involved in the cycle comparing `stmt_edges` to
`callers_in_cycle`, and updates `ssaflags` according to new cycle valid
effects if necessary. This resolves the issue, but ideally, it should be
implemented more safely with the new `edges` format that will be
implemented in the future. For now, this approach should be okay.
aviatesk added a commit that referenced this pull request Jun 6, 2024
#54323 ensures that all frames within a cycle have the
same, cycle valid effects. However, `src.ssaflags` is calculated using
partial effects, so when the effects of a `frame` within the cycle are
updated, there would be an inconsistency between `frame.ipo_effects` and
`frame.src.ssaflags`. Due to this inconsistency, #54323
breaks the test cases from #51092, when backported to
v1.11. On the surface this is because #52999 hasn't been
backported to v1.11, but the fundamental issue lies in this
inconsistency between cycle effects and `ssaflags`.

To resolve this issue, this commit traverses `cycle_backedges` to visit
statements involved in the cycle, and updates each `ssaflags` according
to new cycle valid effects if necessary.
aviatesk added a commit that referenced this pull request Jun 7, 2024
…#54689)

#54323 ensures that all frames within a cycle have the
same, cycle valid effects. However, `src.ssaflags` is calculated using
partial effects, so when the effects of a `frame` within the cycle are
updated, there would be an inconsistency between `frame.ipo_effects` and
`frame.src.ssaflags`. Due to this inconsistency, #54323
breaks the test cases from #51092, when backported to
v1.11. On the surface this is because #52999 hasn't been
backported to v1.11, but the fundamental issue lies in this
inconsistency between cycle effects and `ssaflags`.

To resolve this issue, this commit traverses `cycle_backedges` to visit
statements involved in the cycle, and updates each `ssaflags` according
to new cycle valid effects if necessary.
aviatesk added a commit that referenced this pull request Jun 7, 2024
…#54689)

#54323 ensures that all frames within a cycle have the
same, cycle valid effects. However, `src.ssaflags` is calculated using
partial effects, so when the effects of a `frame` within the cycle are
updated, there would be an inconsistency between `frame.ipo_effects` and
`frame.src.ssaflags`. Due to this inconsistency, #54323
breaks the test cases from #51092, when backported to
v1.11. On the surface this is because #52999 hasn't been
backported to v1.11, but the fundamental issue lies in this
inconsistency between cycle effects and `ssaflags`.

To resolve this issue, this commit traverses `cycle_backedges` to visit
statements involved in the cycle, and updates each `ssaflags` according
to new cycle valid effects if necessary.
@aviatesk aviatesk mentioned this pull request Jun 20, 2024
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DCE bug: unsafe elimination of dead statement, which might not terminate
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