[PATCH] D60395: [InstCombine] Canonicalize (-X s/ Y) to -(X s/ Y)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

Almost there.
Since we never touch the denominator, i think we are always good re vectors.
Does this need rebasing now that the other patch has landed?



================
Comment at: llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll:7
+; CHECK-NEXT:    [[SDIV1:%.*]] = sdiv i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SDIV:%.*]] = sub i32 0, [[SDIV1]]
 ; CHECK-NEXT:    ret i32 [[SDIV]]
----------------
Shouldn't this `sub` also be `nsw`?
```
----------------------------------------
Optimization: nsw preserved
Precondition: true
  %o0 = sub nsw i8 0, %x
  %r = sdiv i8 %o0, %y
=>
  %n0 = sdiv i8 %x, %y
  %r = sub nsw i8 0, %n0

Done: 1
Optimization is correct!

----------------------------------------
Optimization: exact preserved
Precondition: true
  %o0 = sub nsw i8 0, %x
  %r = sdiv exact i8 %o0, %y
=>
  %n0 = sdiv exact i8 %x, %y
  %r = sub i8 0, %n0

Done: 1
Optimization is correct!

----------------------------------------
Optimization: both preserved
Precondition: true
  %o0 = sub nsw i8 0, %x
  %r = sdiv exact i8 %o0, %y
=>
  %n0 = sdiv exact i8 %x, %y
  %r = sub nsw i8 0, %n0

Done: 1
Optimization is correct!

```


================
Comment at: llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll:11
   %neg = sub nsw i32 0, %x
   %sdiv = sdiv i32 %neg, %y
   ret i32 %sdiv
----------------
There is a test that will show that we propagate `exact`?


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D60395/new/

https://reviews.llvm.org/D60395