[Bug tree-optimization/22591] [4.0/4.1 Regression] std::swap() followed by list::erase() produces incorrect list::begin()

[steven at gcc dot gnu dot org]

------- Additional Comments From steven at gcc dot gnu dot org  2005-07-26 
10:43 -------
Well I'll be damned! 
$ ./xgcc -B. t.c -O2 -march=nocona 
$ ./a.out 
Aborted 
$ ./xgcc -B. t.c -O2 -march=nocona -da -fdump-tree-all 
$ ./a.out 
$ 
 
$ ./xgcc -B. t.c -O2 -march=nocona -S -da 
$ mv t.s t.s.with_dumps 
$ ./xgcc -B. t.c -O2 -march=nocona -S 
$ diff -u t.s t.s.with_dumps 
--- t.s 2005-07-26 12:42:14.447531418 +0200 
+++ t.s.with_dumps      2005-07-26 12:42:03.501170603 +0200 
@@ -26,19 +26,20 @@ 
        .type   ListSwap, @function 
 ListSwap: 
 .LFB4: 
-       movq    (%rdi), %rcx 
-       testq   %rcx, %rcx 
+       cmpq    $0, (%rdi) 
        je      .L8 
+       movq    (%rdi), %rdx 
        movq    (%rsi), %rax 
        movq    %rax, (%rdi) 
-       movq    %rcx, (%rsi) 
+       movq    %rdx, (%rsi) 
        movq    8(%rdi), %rdx 
        movq    8(%rsi), %rax 
        movq    %rax, 8(%rdi) 
        movq    %rdx, 8(%rsi) 
+       movq    (%rdi), %rdx 
        movq    8(%rdi), %rax 
        movq    %rdi, (%rax) 
-       movq    %rdi, 8(%rcx) 
+       movq    %rdi, 8(%rdx) 
        movq    (%rsi), %rdx 
        movq    8(%rsi), %rax 
        movq    %rsi, (%rax) 
 
wtf?! 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22591