[llvm-bugs] [Bug 51815] New: Instcombine started loosing inbounds sometimes after 12

via llvm-bugs llvm-bugs at lists.llvm.org
Fri Sep 10 04:08:55 PDT 2021 

https://bugs.llvm.org/show_bug.cgi?id=51815

            Bug ID: 51815
           Summary: Instcombine started loosing inbounds sometimes after
                    12
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: lebedev.ri at gmail.com
                CC: llvm-bugs at lists.llvm.org

https://godbolt.org/z/nP1jTaErz



*** IR Dump Before InstCombinePass on _Z15roundToMultipleIPcET_S1_mb ***
; Function Attrs: inlinehint mustprogress nofree nosync nounwind readnone
uwtable willreturn
define linkonce_odr dso_local i8* @_Z15roundToMultipleIPcET_S1_mb(i8* %value,
i64 %multiple, i1 zeroext %roundDown) local_unnamed_addr #1 comdat {
entry:
  %cmp = icmp eq i64 %multiple, 0
  br i1 %cmp, label %return, label %if.end

if.end:                                           ; preds = %entry
  %0 = ptrtoint i8* %value to i64
  %rem = urem i64 %0, %multiple
  %cmp1 = icmp eq i64 %rem, 0
  br i1 %cmp1, label %return, label %if.end3

if.end3:                                          ; preds = %if.end
  %idx.neg = sub i64 0, %rem
  %add.ptr = getelementptr inbounds i8, i8* %value, i64 %idx.neg
  %add.ptr6 = getelementptr inbounds i8, i8* %add.ptr, i64 %multiple
  %retval.0 = select i1 %roundDown, i8* %add.ptr, i8* %add.ptr6
  br label %return

return:                                           ; preds = %if.end3, %if.end,
%entry
  %retval.2 = phi i8* [ %value, %entry ], [ %retval.0, %if.end3 ], [ %value,
%if.end ]
  ret i8* %retval.2
}


INSTCOMBINE ITERATION #1 on _Z15roundToMultipleIPcET_S1_mb
IC: ADD:   ret i8* %retval.2
IC: ADD:   %retval.2 = phi i8* [ %value, %entry ], [ %retval.0, %if.end3 ], [
%value, %if.end ]
IC: ADD:   br label %return
IC: ADD:   %retval.0 = select i1 %roundDown, i8* %add.ptr, i8* %add.ptr6
IC: ADD:   %add.ptr6 = getelementptr inbounds i8, i8* %add.ptr, i64 %multiple
IC: ADD:   %add.ptr = getelementptr inbounds i8, i8* %value, i64 %idx.neg
IC: ADD:   %idx.neg = sub i64 0, %rem
IC: ADD:   br i1 %cmp1, label %return, label %if.end3
IC: ADD:   %cmp1 = icmp eq i64 %rem, 0
IC: ADD:   %rem = urem i64 %0, %multiple
IC: ADD:   %0 = ptrtoint i8* %value to i64
IC: ADD:   br i1 %cmp, label %return, label %if.end
IC: ADD:   %cmp = icmp eq i64 %multiple, 0
IC: Visiting:   %cmp = icmp eq i64 %multiple, 0
IC: Visiting:   br i1 %cmp, label %return, label %if.end
IC: Visiting:   %0 = ptrtoint i8* %value to i64
IC: Visiting:   %rem = urem i64 %0, %multiple
IC: Visiting:   %cmp1 = icmp eq i64 %rem, 0
IC: Visiting:   br i1 %cmp1, label %return, label %if.end3
IC: Visiting:   %idx.neg = sub i64 0, %rem
Negator: attempting to sink negation into   %rem = urem i64 %0, %multiple
Negator: failed to sink negation into   %rem = urem i64 %0, %multiple
IC: Visiting:   %add.ptr = getelementptr inbounds i8, i8* %value, i64 %idx.neg
IC: Visiting:   %add.ptr6 = getelementptr inbounds i8, i8* %add.ptr, i64
%multiple
IC: Visiting:   %retval.0 = select i1 %roundDown, i8* %add.ptr, i8* %add.ptr6
IC: ADD DEFERRED:   %retval.0.idx = select i1 %roundDown, i64 0, i64 %multiple
IC: Old =   %retval.0 = select i1 %roundDown, i8* %add.ptr, i8* %add.ptr6
    New =   <badref> = getelementptr i8, i8* %add.ptr, i64 %retval.0.idx
IC: ADD:   %retval.0 = getelementptr i8, i8* %add.ptr, i64 %retval.0.idx
IC: ERASE   %1 = select i1 %roundDown, i8* %add.ptr, i8* %add.ptr6
IC: ADD DEFERRED:   %add.ptr = getelementptr inbounds i8, i8* %value, i64
%idx.neg
IC: ADD DEFERRED:   %add.ptr6 = getelementptr inbounds i8, i8* %add.ptr, i64
%multiple
IC: ERASE   %add.ptr6 = getelementptr inbounds i8, i8* %add.ptr, i64 %multiple
IC: ADD:   %add.ptr = getelementptr inbounds i8, i8* %value, i64 %idx.neg
IC: ADD:   %retval.0.idx = select i1 %roundDown, i64 0, i64 %multiple
IC: Visiting:   %retval.0.idx = select i1 %roundDown, i64 0, i64 %multiple
IC: Visiting:   %add.ptr = getelementptr inbounds i8, i8* %value, i64 %idx.neg
IC: Visiting:   %retval.0 = getelementptr i8, i8* %add.ptr, i64 %retval.0.idx
IC: Visiting:   br label %return
IC: Visiting:   %retval.2 = phi i8* [ %value, %entry ], [ %retval.0, %if.end3
], [ %value, %if.end ]
IC: Visiting:   ret i8* %retval.2


INSTCOMBINE ITERATION #2 on _Z15roundToMultipleIPcET_S1_mb
IC: ADD:   ret i8* %retval.2
IC: ADD:   %retval.2 = phi i8* [ %value, %entry ], [ %retval.0, %if.end3 ], [
%value, %if.end ]
IC: ADD:   br label %return
IC: ADD:   %retval.0 = getelementptr i8, i8* %add.ptr, i64 %retval.0.idx
IC: ADD:   %retval.0.idx = select i1 %roundDown, i64 0, i64 %multiple
IC: ADD:   %add.ptr = getelementptr inbounds i8, i8* %value, i64 %idx.neg
IC: ADD:   %idx.neg = sub i64 0, %rem
IC: ADD:   br i1 %cmp1, label %return, label %if.end3
IC: ADD:   %cmp1 = icmp eq i64 %rem, 0
IC: ADD:   %rem = urem i64 %0, %multiple
IC: ADD:   %0 = ptrtoint i8* %value to i64
IC: ADD:   br i1 %cmp, label %return, label %if.end
IC: ADD:   %cmp = icmp eq i64 %multiple, 0
IC: Visiting:   %cmp = icmp eq i64 %multiple, 0
IC: Visiting:   br i1 %cmp, label %return, label %if.end
IC: Visiting:   %0 = ptrtoint i8* %value to i64
IC: Visiting:   %rem = urem i64 %0, %multiple
IC: Visiting:   %cmp1 = icmp eq i64 %rem, 0
IC: Visiting:   br i1 %cmp1, label %return, label %if.end3
IC: Visiting:   %idx.neg = sub i64 0, %rem
Negator: attempting to sink negation into   %rem = urem i64 %0, %multiple
Negator: failed to sink negation into   %rem = urem i64 %0, %multiple
IC: Visiting:   %add.ptr = getelementptr inbounds i8, i8* %value, i64 %idx.neg
IC: Visiting:   %retval.0.idx = select i1 %roundDown, i64 0, i64 %multiple
IC: Visiting:   %retval.0 = getelementptr i8, i8* %add.ptr, i64 %retval.0.idx
IC: Visiting:   br label %return
IC: Visiting:   %retval.2 = phi i8* [ %value, %entry ], [ %retval.0, %if.end3
], [ %value, %if.end ]
IC: Visiting:   ret i8* %retval.2
*** IR Dump After InstCombinePass on _Z15roundToMultipleIPcET_S1_mb ***
; Function Attrs: inlinehint mustprogress nofree nosync nounwind readnone
uwtable willreturn
define linkonce_odr dso_local i8* @_Z15roundToMultipleIPcET_S1_mb(i8* %value,
i64 %multiple, i1 zeroext %roundDown) local_unnamed_addr #1 comdat {
entry:
  %cmp = icmp eq i64 %multiple, 0
  br i1 %cmp, label %return, label %if.end

if.end:                                           ; preds = %entry
  %0 = ptrtoint i8* %value to i64
  %rem = urem i64 %0, %multiple
  %cmp1 = icmp eq i64 %rem, 0
  br i1 %cmp1, label %return, label %if.end3

if.end3:                                          ; preds = %if.end
  %idx.neg = sub i64 0, %rem
  %add.ptr = getelementptr inbounds i8, i8* %value, i64 %idx.neg
  %retval.0.idx = select i1 %roundDown, i64 0, i64 %multiple
  %retval.0 = getelementptr i8, i8* %add.ptr, i64 %retval.0.idx
  br label %return

return:                                           ; preds = %if.end3, %if.end,
%entry
  %retval.2 = phi i8* [ %value, %entry ], [ %retval.0, %if.end3 ], [ %value,
%if.end ]
  ret i8* %retval.2
}

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