[llvm-bugs] [Bug 31251] New: AVX512 Loop Vectorizer introduces non-dominating instruction

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31251

            Bug ID: 31251
           Summary: AVX512 Loop Vectorizer introduces non-dominating
                    instruction
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Loop Optimizer
          Assignee: unassignedbugs at nondot.org
          Reporter: kfischer at college.harvard.edu
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Bugpoint reduced test case:
```
; ModuleID = 'bugpoint-reduced-simplified.bc'
source_filename = "bugpoint-output-1d9ce6e.bc"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%Dual.212 = type { %Dual.213, %Partials.215 }
%Dual.213 = type { double, %Partials.214 }
%Partials.214 = type { [2 x double] }
%Partials.215 = type { [2 x %Dual.213] }

; Function Attrs: sspreq
define void @"julia_axpy!_65480"(%Dual.212*) #0 {
top:
  br label %if24

if24:                                             ; preds = %if24, %top
  %"#temp#1.sroa.3.02" = phi i64 [ undef, %top ], [ %2, %if24 ]
  %"#temp#1.sroa.0.01" = phi i64 [ undef, %top ], [ %1, %if24 ]
  %1 = add i64 %"#temp#1.sroa.0.01", 1
  %2 = add i64 %"#temp#1.sroa.3.02", 1
  %v2.sroa.0.0..sroa_cast = bitcast %Dual.212* %0 to i64*
  %v2.sroa.0.0.copyload = load i64, i64* %v2.sroa.0.0..sroa_cast, align 1
  %3 = add i64 %"#temp#1.sroa.0.01", -1
  %4 = getelementptr inbounds %Dual.212, %Dual.212* undef, i64 %3, i32 1, i32
0, i64 0, i32 1, i32 0, i64 0
  %5 = bitcast double* %4 to i64*
  store i64 undef, i64* %5, align 8
  %notlhs27 = icmp eq i64 %2, undef
  %notrhs28 = icmp eq i64 %1, undef
  %6 = or i1 %notrhs28, %notlhs27
  br i1 %6, label %L41.L335_crit_edge, label %if24

L41.L335_crit_edge:                               ; preds = %if24
  ret void
}

attributes #0 = { sspreq "no-frame-pointer-elim"="true" "target-cpu"="knl" }

!llvm.module.flags = !{!0}

!0 = !{i32 1, !"Debug Info Version", i32 3}
```
```
$ opt -loop-vectorize bug.ll
Instruction does not dominate all uses!
  %v2.sroa.0.0..sroa_cast = bitcast %Dual.212* %0 to i64*
  %bc = bitcast i64* %v2.sroa.0.0..sroa_cast to i8*
Instruction does not dominate all uses!
  %v2.sroa.0.0..sroa_cast = bitcast %Dual.212* %0 to i64*
  %bc1 = bitcast i64* %v2.sroa.0.0..sroa_cast to i8*
```

Working on a patch.

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