[PATCH] D114666: [InstSimplify] Fold bool(X) ^ 1 == 0 to X

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


================
Comment at: llvm/lib/Analysis/InstructionSimplify.cpp:2692
 
   // A boolean compared to true/false can be simplified in 14 out of the 20
+
----------------
The comment and code structure suggest that we are missing related patterns. 

Can we generalize this to look through a 'not' of LHS and invert/swap the predicate?

For example, we should be able to reduce these patterns too:
```
define i1 @not_cmp_ne(i1 %x) {
  %not = xor i1 %x, true
  %cmp = icmp ne i1 %not, true
  ret i1 %cmp
}

define i1 @not_cmp_ult(i1 %x) {
  %not = xor i1 %x, true
  %cmp = icmp ult i1 %not, 1
  ret i1 %cmp
}

```


================
Comment at: llvm/test/Transforms/InstSimplify/icmp.ll:194
+  %not = xor i1 %x, true
+  %t0 = sext i1 %not to i32
+  %cmp = icmp eq i32 %t0, 0
----------------
We want tests with the sext instruction because this code handles looking through that cast (and possible others?), but the minimal pattern does not include casts. So we need to add tests for code with no sext ops.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D114666/new/

https://reviews.llvm.org/D114666