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implementation
; edgefailure - This function illustrates how SCCP is not doing it's job. This
; function should be optimized almost completely away: the loop should be
; analyzed to detect that the body executes exactly once, and thus the branch
; can be eliminated and code becomes trivially dead. This is distilled from a
; real benchmark (mst from Olden benchmark, MakeGraph function). When SCCP is
; fixed, this should be eliminated by a single SCCP application. TODO
;
int *"edgefailure"()
begin
bb1:
%A = malloc int
br label %bb2
bb2:
%i = phi int [ %i2, %bb2 ], [ 0, %bb1 ] ;; Always 0
%i2 = add int %i, 1 ;; Always 1
store int %i, int *%A
%loop = setle int %i2, 0 ;; Always false
br bool %loop, label %bb2, label %bb3
bb3:
ret int * %A
end
int "test function"(int %i0, int %j0)
%i1 = const int 1
%j1 = const int 1
%k1 = const int 0
begin
BB1:
br label %BB2
BB2:
%j2 = phi int [%j4, %BB7], [%j1, %BB1]
%k2 = phi int [%k4, %BB7], [%k1, %BB1]
%kcond = setlt int %k2, 100
br bool %kcond, label %BB3, label %BB4
BB3:
%jcond = setlt int %j2, 20
br bool %jcond, label %BB5, label %BB6
BB4:
ret int %j2
BB5:
%k3 = add int %k2, 1
br label %BB7
BB6:
%k5 = add int %k2, 1
br label %BB7
BB7:
%j4 = phi int [%i1, %BB5], [%k2, %BB6]
%k4 = phi int [%k3, %BB5], [%k5, %BB6]
br label %BB2
end
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