https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63224
--- Comment #8 from Sebastian Huber <sebastian.hu...@embedded-brains.de> ---
Actually the for loop is not necessary.
int bar(int s, int *a)
{
int c;
int r;
r = s != 0 && (c = a[s]);
if (s == 2 && c == 0) {
} else if (s != 0) {
return 0;
}
return r;
}
cp test.c Os.c
cp test.c O2.c
arm-rtems4.11-gcc -Wfatal-errors -Wall -Os -S Os.c -o Os.s
-fdump-tree-all-all-lineno
Os.c: In function 'bar':
Os.c:8:18: warning: 'c' may be used uninitialized in this function
[-Wmaybe-uninitialized]
if (s == 2 && c == 0) {
^
arm-rtems4.11-gcc -Wfatal-errors -Wall -O2 -S O2.c -o O2.s
-fdump-tree-all-all-lineno
diff -u O*c*uni*
--- O2.c.140t.uninit1 2014-09-12 09:29:10.627991057 +0200
+++ Os.c.140t.uninit1 2014-09-12 09:29:10.574991191 +0200
@@ -5,6 +5,9 @@
Pass statistics:
----------------
+[WORKLIST]: add to initial list: c_1 = PHI <c_5(D)(7), c_11(3)>
+[CHECK]: examining phi: c_1 = PHI <c_5(D)(7), c_11(3)>
+[CHECK]: Found unguarded use: _13 = c_1 == 0;
Pass statistics:
----------------
@@ -13,13 +16,97 @@
{
intD.3 rD.4078;
intD.3 cD.4077;
+ intD.3 _3;
+ unsigned intD.6 s.1_6;
+ unsigned intD.6 _7;
+ intD.3 * _9;
+ _BoolD.1375 _12;
+ _BoolD.1375 _13;
+ _BoolD.1375 _14;
+ _BoolD.1375 _16;
+ _BoolD.1375 _18;
;; basic block 2, loop depth 0, count 0, freq 10000, maybe hot
-;; prev block 0, next block 1, flags: (NEW, REACHABLE)
+;; prev block 0, next block 7, flags: (NEW, REACHABLE)
;; pred: ENTRY [100.0%] (FALLTHRU,EXECUTABLE)
+;; starting at line 6
+ [Os.c : 6:13] if (s_4(D) != 0)
+ goto <bb 3>;
+ else
+ goto <bb 7>;
+;; succ: 3 [50.0%] (TRUE_VALUE,EXECUTABLE)
+;; 7 [50.0%] (FALSE_VALUE,EXECUTABLE)
+
+;; basic block 7, loop depth 0, count 0, freq 5000, maybe hot
+;; prev block 2, next block 3, flags: (NEW)
+;; pred: 2 [50.0%] (FALSE_VALUE,EXECUTABLE)
+;;
+ goto <bb 4>;
+;; succ: 4 [100.0%] (FALLTHRU)
+
+;; basic block 3, loop depth 0, count 0, freq 5000, maybe hot
+;; prev block 7, next block 4, flags: (NEW, REACHABLE)
+;; pred: 2 [50.0%] (TRUE_VALUE,EXECUTABLE)
+;; starting at line 6, discriminator 1
+ [Os.c : 6:22] # RANGE [1, 4294967295]
+ s.1_6 = (unsigned intD.6) s_4(D);
+ [Os.c : 6:22] # RANGE [0, 4294967295] NONZERO 0x000000000fffffffc
+ _7 = s.1_6 * 4;
+ [Os.c : 6:22] # PT = nonlocal
+ _9 = a_8(D) + _7;
+ [Os.c : 6:19] # VUSE <.MEM_10(D)>
+ c_11 = [Os.c : 6] *_9;
+ [Os.c : 6:13] # RANGE [0, 1]
+ _16 = c_11 != 0;
+ [Os.c : 6:13] # RANGE [0, 1] NONZERO 0x00000000000000001
+ r_19 = (intD.3) _16;
+;; succ: 4 [100.0%] (FALLTHRU,EXECUTABLE)
+
+;; basic block 4, loop depth 0, count 0, freq 10000, maybe hot
+;; prev block 3, next block 8, flags: (NEW, REACHABLE)
+;; pred: 7 [100.0%] (FALLTHRU)
+;; 3 [100.0%] (FALLTHRU,EXECUTABLE)
+;; starting at line 8, discriminator 6
+ # c_1 = PHI <c_5(D)(7), c_11(3)>
+ # RANGE [0, 1] NONZERO 0x00000000000000001
+ # r_2 = PHI <[Os.c : 6:13] 0(7), [Os.c : 6:13] r_19(3)>
+ [Os.c : 8:8] # RANGE [0, 1]
+ _12 = s_4(D) == 2;
+ [Os.c : 8:18] # RANGE [0, 1]
+ _13 = c_1 == 0;
+ [Os.c : 8:13] # RANGE [0, 1]
+ _14 = _13 & _12;
+ [Os.c : 9:12] # RANGE [0, 1]
+ _18 = s_4(D) != 0;
+ [Os.c : 9:12] if (_14 < _18)
+ goto <bb 5>;
+ else
+ goto <bb 8>;
+;; succ: 5 [39.0%] (TRUE_VALUE,EXECUTABLE)
+;; 8 [61.0%] (FALSE_VALUE,EXECUTABLE)
+
+;; basic block 8, loop depth 0, count 0, freq 6100, maybe hot
+;; prev block 4, next block 5, flags: (NEW)
+;; pred: 4 [61.0%] (FALSE_VALUE,EXECUTABLE)
+;;
+ goto <bb 6>;
+;; succ: 6 [100.0%] (FALLTHRU)
+
+;; basic block 5, loop depth 0, count 0, freq 3900, maybe hot
+;; prev block 8, next block 6, flags: (NEW)
+;; pred: 4 [39.0%] (TRUE_VALUE,EXECUTABLE)
+;;
+;; succ: 6 [100.0%] (FALLTHRU,EXECUTABLE)
+
+;; basic block 6, loop depth 0, count 0, freq 10000, maybe hot
+;; prev block 5, next block 1, flags: (NEW, REACHABLE)
+;; pred: 5 [100.0%] (FALLTHRU,EXECUTABLE)
+;; 8 [100.0%] (FALLTHRU)
;; starting at line -1
+ # RANGE [0, 1] NONZERO 0x00000000000000001
+ # _3 = PHI <[Os.c : 10:3] 0(5), [Os.c : 13:2] r_2(8)>
# VUSE <.MEM_10(D)>
- return 0;
+ return _3;
;; succ: EXIT [100.0%]
}
