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11 Commits

Author SHA1 Message Date
Bjorn Pettersson
acdc419c89 [test] Use -passes=instcombine instead of -instcombine in lots of tests. NFC 
Another step moving away from the deprecated syntax of specifying
pass pipeline in opt.

Differential Revision: https://reviews.llvm.org/D119081
 2022-02-07 14:26:59 +01:00
Sanjay Patel
7bb8bfa062 [InstCombine] fix miscompile from vector select substitution 
This is similar to the fix in c590a9880d7a ( PR49832 ), but
we missed handling the pattern for select of bools (no compare
inst).

We can't substitute a vector value because the equality condition
replacement that we are attempting requires that the condition
is true/false for the entire value. Vector select can be partly
true/false.

I added an assert for vector types, so we shouldn't hit this again.
Fixed formatting while auditing the callers.

https://llvm.org/PR50500
 2021-05-30 07:11:58 -04:00
Juneyoung Lee
8a156d1c27 [InstCombine] Fully disable select to and/or i1 folding 
This is a patch that disables the poison-unsafe select -> and/or i1 folding.

It has been blocking D72396 and also has been the source of a few miscompilations
described in llvm.org/pr49688 .
D99674 conditionally blocked this folding and successfully fixed the latter one.
The former one was still blocked, and this patch addresses it.

Note that a few test functions that has `_logical` suffix are now deoptimized.
These are created by @nikic to check the impact of disabling this optimization
by copying existing original functions and replacing and/or with select.

I can see that most of these are poison-unsafe; they can be revived by introducing
freeze instruction. I left comments at fcmp + select optimizations (or-fcmp.ll, and-fcmp.ll)
because I think they are good targets for freeze fix.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D101191
 2021-05-06 09:29:52 +09:00
Juneyoung Lee
24ce194cfe [InstCombine] generalize select + select/and/or folding using implied conditions 
This patch optimizes the remaining possible cases in D101191 by generalizing isImpliedCondition()-based
foldings.

Assume that there is `op a, (select b, _, _)` where op is one of `and i1`, `or i1` or their select forms.

We can do the following optimization based on the result of `isImpliedCondition(a, b)`:

If a = true implies…
- b = true:
    - select a, (select b, A, B), false => select a, A, false : https://alive2.llvm.org/ce/z/WCnZYh
    - and a, (select b, A, B) => select a, A, false : https://alive2.llvm.org/ce/z/uZhcMG
- b = false:
    - select a, (select b, A, B), false => select a, B, false : https://alive2.llvm.org/ce/z/c2hJpV
    - and a, (select b, A, B) => select a, B, false : https://alive2.llvm.org/ce/z/5ggwMM

If a = false implies…
- b = true:
    - select a, true, (select b, A, B) => select a, true, A : https://alive2.llvm.org/ce/z/tidKvH
    - or a, (select b, A, B) =>  select a, true, A : https://alive2.llvm.org/ce/z/cC-uyb
- b = false:
    - select a, true, (select b, A, B) => select a, true, B : https://alive2.llvm.org/ce/z/ZXpJq9
    - or a, (select b, A, B) => select a, true, B : https://alive2.llvm.org/ce/z/hnDrJj

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D101720
 2021-05-04 09:42:06 +09:00
Juneyoung Lee
960a767368 Reland "[InstCombine] Add simplification of two logical and/ors" 
This relands 07c3b97e184d5bd828b8a680cdce46e73f3db9fc (D96945) which was reverted by
commit f49354838e526671e616d16199ebdee653b9f6fa.
The two-stage compilation successfully tests passes on my machine.
 2021-03-23 16:24:50 +09:00
Juneyoung Lee
f49354838e Revert "[InstCombine] Add simplification of two logical and/ors" 
This reverts commit 07c3b97e184d5bd828b8a680cdce46e73f3db9fc due to a reported failure in two-stage build.
 2021-03-10 05:48:31 +09:00
Juneyoung Lee
07c3b97e18 [InstCombine] Add simplification of two logical and/ors 
This is a patch that adds folding of two logical and/ors that share one variable:

a && (a && b) -> a && b
a && (a & b)  -> a && b
...

This is towards removing the poison-unsafe select optimization (D93065 has more context).

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D96945
 2021-03-08 02:38:43 +09:00
Juneyoung Lee
33590ed4f2 [InstCombine] fix another poison-unsafe select transformation 
This fixes another unsafe select folding by disabling it if
EnableUnsafeSelectTransform is set to false.

EnableUnsafeSelectTransform's default value is true, hence it won't
affect generated code (unless the flag is explicitly set to false).
 2021-03-08 02:11:04 +09:00
Juneyoung Lee
d65c947600 [InstCombine] enrich select-safe-bool-transforms.ll test (NFC) 
for https://reviews.llvm.org/D96945
 2021-03-08 00:01:08 +09:00
Juneyoung Lee
2c16c4a43c [ValueTracking] update directlyImpliesPoison to look into select's condition 
This is a minor update in directlyImpliesPoison and makes it look into select's
condition.
Splitted from https://reviews.llvm.org/D96945
 2021-03-07 23:16:44 +09:00
Juneyoung Lee
5260873c3b [InstCombine] add tests for simplification of logical and/ors (NFC) 2021-02-18 17:42:06 +09:00