https://bugs.llvm.org/show_bug.cgi?id=48533
Bug ID: 48533
Summary: builtin longjmp miscompiled when jmpbuf is
rbp-relative address
Product: new-bugs
Version: 10.0
Hardware: PC
OS: FreeBSD
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: j...@mit.edu
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org
Created attachment 24293
--> https://bugs.llvm.org/attachment.cgi?id=24293&action=edit
bitcode that llc miscompiles
If the address argument to __builtin_longjmp is %rbp-relative the longjmp is
miscompiled. If I compile the attached .ll file with the 10.0 llc the function
ends
movq -48(%rbp), %rbp
movq -40(%rbp), %rax # This load needs the original rbp
movq -32(%rbp), %rsp # This load needs the original rbp
jmpq *%rax
Note that the first instruction overwrites %rbp but the next two instructions
depend on the old value. The branch goes to a random address with a random
%rsp.
The same bug is present in the version of llvm 11 included with FreeBSD-CURRENT
(13.0).
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