[llvm-bugs] [Bug 47709] New: [LICM] Invariant llvm.memcpy is not hoisted out of loop.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47709

            Bug ID: 47709
           Summary: [LICM] Invariant llvm.memcpy is not hoisted out of
                    loop.
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Loop Optimizer
          Assignee: unassignedbugs at nondot.org
          Reporter: florian_hahn at apple.com
                CC: llvm-bugs at lists.llvm.org

In the example below, both operands of the llvm.memcpy calls are loop-invariant
and do not alias. They should be hoisted out of the loop, but are not.


define i32 @main(i8* %ptr.0) {
entry:
  %identity = alloca [48 x i8], align 4
  %identity.0 = bitcast [48 x i8]* %identity to i8*
  %identity.1 = getelementptr inbounds [48 x i8], [48 x i8]* %identity, i64 0,
i64 16
  %identity.2 = getelementptr inbounds [48 x i8], [48 x i8]* %identity, i64 0,
i64 32
  call void @llvm.memset.p0i8.i64(i8* nonnull align 4 dereferenceable(16)
%identity.0, i8 0, i64 16, i1 false)
  call void @llvm.memset.p0i8.i64(i8* nonnull align 4 dereferenceable(16)
%identity.1, i8 0, i64 16, i1 false)
  call void @llvm.memset.p0i8.i64(i8* nonnull align 4 dereferenceable(16)
%identity.2, i8 0, i64 16, i1 false)
  %ptr.1 = getelementptr inbounds i8, i8* %ptr.0, i64 16
  %ptr.2 = getelementptr inbounds i8, i8* %ptr.0, i64 32
  br label %loop

loop:                                             ; preds = %loop, %entry
  %run.096 = phi i32 [ 0, %entry ], [ %inc.1, %loop ]
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 4 dereferenceable(16)
%ptr.0, i8* nonnull align 4 dereferenceable(16) %identity.0, i64 16, i1 false)
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 4 dereferenceable(16)
%ptr.1, i8* nonnull align 4 dereferenceable(16) %identity.1, i64 16, i1 false)
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 4 dereferenceable(16)
%ptr.2, i8* nonnull align 4 dereferenceable(16) %identity.2, i64 16, i1 false)
  %inc.1 = add nuw nsw i32 %run.096, 1
  %exitcond98.not = icmp eq i32 %run.096, 24
  br i1 %exitcond98.not, label %exit, label %loop

exit:                                             ; preds = %loop
  ret i32 1
}

; Function Attrs: argmemonly nounwind willreturn writeonly
declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i1 immarg)
#0

; Function Attrs: argmemonly nounwind willreturn
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8*
noalias nocapture readonly, i64, i1 immarg) #1

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