http://llvm.org/bugs/show_bug.cgi?id=5977
Summary: llc generates incorrect exception handling tables when
generating PIC code
Product: libraries
Version: trunk
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: Common Code Generator Code
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Created an attachment (id=4012)
--> (http://llvm.org/bugs/attachment.cgi?id=4012)
testcase
To reproduce (on amd64 linux):
llc -f -relocation-model=pic -o temp.s temp.bc
The generated assembly contains:
.byte 0x9B # @TType format
(indirect pcrel sdata4)
and later:
.quad type_info_1 # TypeInfo
the two don't match, also the TType Base Offset is wrong too, since it assumes
that TypeInfo entries are 4 byte long, which is not true on amd64.
I think this is caused by this code in DwarfException.cpp:
if (LSDASection->getKind().isWriteable() ||
Asm->TM.getRelocationModel() == Reloc::Static)
TTypeFormat = dwarf::DW_EH_PE_absptr;
else
TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
Here, the else part is executed, but later, the typeinfo is emitted as:
O << Asm->Mang->getMangledName(GV);
I think the fix is to always use absptr, the ELF linker can and does fixup the
type info even if the section it is in is read-only.
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