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From: "congli at smail dot nju.edu.cn" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/114206] New: GCC generates wrong-code Date: Sat, 02 Mar 2024 09:06:24 +0000 [thread overview] Message-ID: <bug-114206-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114206 Bug ID: 114206 Summary: GCC generates wrong-code Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: congli at smail dot nju.edu.cn Target Milestone: --- The program shown below presents a wrong code bug, where the correct results should be "f(0, NULL) = 0" while `-Os -fno-tree-ccp -fno-tree-copy-prop -fno-tree-forwprop -fno-tree-fre -fno-tree-vrp` prints "f(0, NULL) = 1". ``` #include <stdio.h> int f(int t, const int *a) { const int b[4] = {0}; if (t == 0) { return f(1, b); } else { return b == a; } } int main(void) { printf("f(0, NULL) = %d\n", f(0, NULL)); } ``` Compiler Explorer: https://gcc.godbolt.org/z/W164xWMrP We checked the assembly, finding that it is weird that the compiler generates a `cmove` instruction. See explanations below: ``` f: leaq -16(%rsp), %rax -> RAX = RSP-16 testl %edi, %edi -> we called f(0, NULL); %edi = 0, ZF = 1 cmove %rax, %rsi -> condition fulfilled; RSI=RAX=RSP-16; weird generation cmpq %rax, %rsi -> RSI=RAX; ZF=1 sete %al -> AL = 1 movzbl %al, %eax -> EAX = 1 (error) ret ```
next reply other threads:[~2024-03-02 9:06 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-03-02 9:06 congli at smail dot nju.edu.cn [this message] 2024-03-02 9:13 ` [Bug tree-optimization/114206] " pinskia at gcc dot gnu.org 2024-03-02 9:27 ` [Bug tree-optimization/114206] recursive function call vs local variable addresses congli at smail dot nju.edu.cn 2024-03-02 9:36 ` congli at smail dot nju.edu.cn 2024-03-02 11:06 ` xry111 at gcc dot gnu.org 2024-03-02 15:15 ` arsen at gcc dot gnu.org 2024-03-04 9:54 ` rguenth at gcc dot gnu.org 2024-03-04 17:31 ` [Bug tree-optimization/114206] [11/12/13/14 Regression] " pinskia at gcc dot gnu.org 2024-03-05 12:14 ` jakub at gcc dot gnu.org
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