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145
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1 /* PR c/71924 - missing -Wreturn-local-addr returning alloca result
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2 Test derived from gcc.c-torture/execute/20071108-1.c. It shows
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3 a false positive at -Os caused by the jump threading/vrp1 pass.
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4 { dg-do compile }
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5 { dg-options "-Os -fdump-tree-optimized" } */
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6
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7 struct S
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8 {
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9 int i;
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10 };
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11
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12 void* f (void);
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13
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14 __attribute__ ((noinline))
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15 struct S* g (int i)
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16 {
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17 struct S *p = f (), q;
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18
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19 if (p == 0)
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20 p = &q;
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21
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22 p->i = i;
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23
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24 if (p == &q)
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25 p = 0;
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26
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27 /* With -Os the warning pass sees:
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28
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29 ...
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30 <bb 4>
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31 # p_1 = PHI <&q(2), p_5(3)>
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32 p_1->i = i_6(D);
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33 if (&q == p_1)
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34 goto <bb 6>; [14.90%]
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35 else
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36 goto <bb 5>; [85.10%]
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37
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38 <bb 5>
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39
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40 <bb 6>
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41 # p_2 = PHI <0B(4), p_1(5)>
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42 q ={v} {CLOBBER};
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43 return p_2;
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44 }
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45
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46 which leads to: */
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47 return p; /* { dg-bogus "may return address of local variable" "" { xfail *-*-* } } */
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48
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49 /* Whereas as -O2 the pass sees:
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50
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51 <bb 2>
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52 p_5 = f ();
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53 if (p_5 == 0B)
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54 goto <bb 4>; [30.00%]
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55 else
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56 goto <bb 3>; [70.00%]
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57
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58 <bb 3>
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59 # p_2 = PHI <0B(5), p_5(4)>
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60 q ={v} {CLOBBER};
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61 return p_2;
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62
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63 <bb 4>
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64 p_5->i = i_6(D);
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65 goto <bb 3>; [100.00%]
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66
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67 <bb 5>
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68 q.i = i_6(D);
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69 goto <bb 3>; [100.00%]
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70 }
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71
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72 and no warning. */
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73 }
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