[PATCH] D71690: [SCEV] get a more accurate range for AddRecExpr with nuw flag

[ChenZheng via Phabricator via llvm-commits]

shchenz marked an inline comment as done.
shchenz added inline comments.


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Comment at: llvm/test/Analysis/ScalarEvolution/range_nw_flag.ll:23
 ; CHECK-LABEL: @test-addrec-nuw
-; CHECK: -->  {(1 + (10 smax %offset))<nuw>,+,1}<nuw><%loop> U: full-set S: full-set 
+; CHECK: -->  {(1 + (10 smax %offset))<nuw>,+,1}<nuw><%loop> U: [11,0) S: full-set
 define void @test-addrec-nuw(float* %input, i32 %offset, i32 %numIterations) {
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For signed range, I think here it should also be [11,0).
but seems, there is a legacy issue for start SCEV signed range: `{(1 + (10 smax %offset))<nuw>,+,1}<nuw><%loop>`.
 
signed range for  `(10 smax %offset)` is  `[10, SINT_MIN)`

`(1 + (10 smax %offset))<nuw>` signed range should be `[11, SINT_MIN)`, instead of full-set? @nikic 

Even with the change in https://reviews.llvm.org/D64869 which takes `nuw` for add into account, we still get full-set as result.
Flow in `addWithNoWrap`:
normal add result for (1 + [10, SINT_MIN))<nuw> is `[11, SINT_MIN +1)`
uadd_sat result for (1 + [10, SINT_MIN))<nuw> is also `[11, SINT_MIN +1)`, so final result is `[11, SINT_MIN +1)`, currently this range is treated as signed wrap range. (Min value is not SINT_MIN)



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  https://reviews.llvm.org/D71690/new/

https://reviews.llvm.org/D71690