[PATCH] D60846: [ValueTracking] Improve isKnowNonZero for Ints

[Mikael Holmén via Phabricator via llvm-commits]

uabelho added a comment.

This is as far as I've come:

With

opt -S -o - red.ll -simplifycfg -loop-unroll

I get

; ModuleID = 'red.ll'
source_filename = "red.ll"

declare void @foo(i16)

define i16 @main() {

  br label %bb1

bb1:                                              ; preds = %0

  call void @foo(i16 0)
  call void @foo(i16 1000)
  ret i16 0

}

which I think is correct, and with

opt -S -o - red.ll -instcombine -simplifycfg -loop-unroll

I get

; ModuleID = 'red.ll'
source_filename = "red.ll"

declare void @foo(i16)

define i16 @main() {

  br label %bb1

bb1:                                              ; preds = %0

  call void @foo(i16 0)
  call void @foo(i16 1)
  ret i16 0

}

which I think is incorrect.

And in both cases red.ll is

declare void @foo(i16)

define i16 @main() {

  br label %bb1

bb1:                                              ; preds = %bb9, %0

  %i.3.0 = phi i16 [ 0, %0 ], [ %_tmp19, %bb9 ]
  %_tmp8 = icmp uge i16 %i.3.0, 1
  br i1 %_tmp8, label %bb3, label %bb5

bb3:                                              ; preds = %bb1

  %_tmp11 = add i16 1, 1
  %_tmp12 = icmp ult i16 %i.3.0, %_tmp11
  br i1 %_tmp12, label %bb4, label %bb5

bb4:                                              ; preds = %bb3

  br label %bb6

bb5:                                              ; preds = %bb3, %bb1

  br label %bb6

bb6:                                              ; preds = %bb5, %bb4

  %tmp0.5.0 = phi i16 [ 1, %bb4 ], [ 0, %bb5 ]
  %_tmp14 = icmp ne i16 %tmp0.5.0, 0
  br i1 %_tmp14, label %bb7, label %bb8

bb7:                                              ; preds = %bb6

  br label %bb9

bb8:                                              ; preds = %bb6

  br label %bb9

bb9:                                              ; preds = %bb8, %bb7

  %tmp1.6.0 = phi i16 [ 1000, %bb7 ], [ %i.3.0, %bb8 ]
  call void @foo(i16 %tmp1.6.0)
  %_tmp19 = add i16 %i.3.0, 1
  %_tmp21 = icmp ult i16 %_tmp19, 2
  br i1 %_tmp21, label %bb1, label %bb10

bb10:                                             ; preds = %bb9

  ret i16 0

}

If I revert this commit I get

  call void @foo(i16 0)
  call void @foo(i16 1000)

in both cases.


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D60846/new/

https://reviews.llvm.org/D60846