[LLVMbugs] [Bug 783] NEW: llvm-gcc[34] i386 ELF ABI struct return incompatibility

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=783

           Summary: llvm-gcc[34] i386 ELF ABI struct return incompatibility
           Product: tools
           Version: 1.7
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: llvm-gcc
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sabre at nondot.org


The ELF ABI specifies that struct returns are passed as a hidden first argument (we get this right).

However, the pointer itself is also supposed to be returned from the function in EAX.  Thus, llvm-gcc 
should compile:

struct X { int A, B; };
struct X foo() {}

to:

%struct.X* %foo(%struct.X* %agg.result) {  
        ret %struct.X* %agg.result
}

instead of:

void %foo(%struct.X* %agg.result) {  
        ret void
}

In practice, this is unlikely to make a difference, but it is still an ABI bug.   This affects both llvm-gcc3 
and llvm-gcc4.

-Chris



------- You are receiving this mail because: -------
You are on the CC list for the bug, or are watching someone who is.