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      1 ; RUN: opt < %s -tailcallelim -S | not grep call
      2 ; PR4323
      3 
      4 ; Several cases where tail call elimination should move the load above the call,
      5 ; then eliminate the tail recursion.
      6 
      7 
      8 @global = external global i32		; <i32*> [#uses=1]
      9 @extern_weak_global = extern_weak global i32		; <i32*> [#uses=1]
     10 
     11 
     12 ; This load can be moved above the call because the function won't write to it
     13 ; and the call has no side effects.
     14 define fastcc i32 @raise_load_1(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) nounwind readonly {
     15 entry:
     16 	%tmp2 = icmp sge i32 %start_arg, %a_len_arg		; <i1> [#uses=1]
     17 	br i1 %tmp2, label %if, label %else
     18 
     19 if:		; preds = %entry
     20 	ret i32 0
     21 
     22 else:		; preds = %entry
     23 	%tmp7 = add i32 %start_arg, 1		; <i32> [#uses=1]
     24 	%tmp8 = call fastcc i32 @raise_load_1(i32* %a_arg, i32 %a_len_arg, i32 %tmp7)		; <i32> [#uses=1]
     25 	%tmp9 = load i32* %a_arg		; <i32> [#uses=1]
     26 	%tmp10 = add i32 %tmp9, %tmp8		; <i32> [#uses=1]
     27 	ret i32 %tmp10
     28 }
     29 
     30 
     31 ; This load can be moved above the call because the function won't write to it
     32 ; and the load provably can't trap.
     33 define fastcc i32 @raise_load_2(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) readonly {
     34 entry:
     35 	%tmp2 = icmp sge i32 %start_arg, %a_len_arg		; <i1> [#uses=1]
     36 	br i1 %tmp2, label %if, label %else
     37 
     38 if:		; preds = %entry
     39 	ret i32 0
     40 
     41 else:		; preds = %entry
     42 	%nullcheck = icmp eq i32* %a_arg, null		; <i1> [#uses=1]
     43 	br i1 %nullcheck, label %unwind, label %recurse
     44 
     45 unwind:		; preds = %else
     46 	unreachable
     47 
     48 recurse:		; preds = %else
     49 	%tmp7 = add i32 %start_arg, 1		; <i32> [#uses=1]
     50 	%tmp8 = call fastcc i32 @raise_load_2(i32* %a_arg, i32 %a_len_arg, i32 %tmp7)		; <i32> [#uses=1]
     51 	%tmp9 = load i32* @global		; <i32> [#uses=1]
     52 	%tmp10 = add i32 %tmp9, %tmp8		; <i32> [#uses=1]
     53 	ret i32 %tmp10
     54 }
     55 
     56 
     57 ; This load can be safely moved above the call (even though it's from an
     58 ; extern_weak global) because the call has no side effects.
     59 define fastcc i32 @raise_load_3(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) nounwind readonly {
     60 entry:
     61 	%tmp2 = icmp sge i32 %start_arg, %a_len_arg		; <i1> [#uses=1]
     62 	br i1 %tmp2, label %if, label %else
     63 
     64 if:		; preds = %entry
     65 	ret i32 0
     66 
     67 else:		; preds = %entry
     68 	%tmp7 = add i32 %start_arg, 1		; <i32> [#uses=1]
     69 	%tmp8 = call fastcc i32 @raise_load_3(i32* %a_arg, i32 %a_len_arg, i32 %tmp7)		; <i32> [#uses=1]
     70 	%tmp9 = load i32* @extern_weak_global		; <i32> [#uses=1]
     71 	%tmp10 = add i32 %tmp9, %tmp8		; <i32> [#uses=1]
     72 	ret i32 %tmp10
     73 }
     74 
     75 
     76 ; The second load can be safely moved above the call even though it's from an
     77 ; unknown pointer (which normally means it might trap) because the first load
     78 ; proves it doesn't trap.
     79 define fastcc i32 @raise_load_4(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) readonly {
     80 entry:
     81 	%tmp2 = icmp sge i32 %start_arg, %a_len_arg		; <i1> [#uses=1]
     82 	br i1 %tmp2, label %if, label %else
     83 
     84 if:		; preds = %entry
     85 	ret i32 0
     86 
     87 else:		; preds = %entry
     88 	%nullcheck = icmp eq i32* %a_arg, null		; <i1> [#uses=1]
     89 	br i1 %nullcheck, label %unwind, label %recurse
     90 
     91 unwind:		; preds = %else
     92 	unreachable
     93 
     94 recurse:		; preds = %else
     95 	%tmp7 = add i32 %start_arg, 1		; <i32> [#uses=1]
     96 	%first = load i32* %a_arg		; <i32> [#uses=1]
     97 	%tmp8 = call fastcc i32 @raise_load_4(i32* %a_arg, i32 %first, i32 %tmp7)		; <i32> [#uses=1]
     98 	%second = load i32* %a_arg		; <i32> [#uses=1]
     99 	%tmp10 = add i32 %second, %tmp8		; <i32> [#uses=1]
    100 	ret i32 %tmp10
    101 }
    102