Tweak the MCExternalSymbolizer to not use the SymbolLookUp() call back
to not guess at a symbol name in some cases.
The problem is that in object files assembled starting at address 0, when
trying to symbolicate something that starts like this:
% cat x.s
_t1:
vpshufd $0x0, %xmm1, %xmm0
the symbolic disassembly can end up like this:
% otool -tV x.o
x.o:
(__TEXT,__text) section
_t1:
0000000000000000 vpshufd $_t1, %xmm1, %xmm0
Which is in this case produced incorrect symbolication.
But it is useful in some cases to use the SymbolLookUp() call back
to guess at some immediate values. For example one like this
that does not have an external relocation entry:
% cat y.s
_t1:
movl $_d1, %eax
.data
_d1: .long 0
% clang -c -arch i386 y.s
% otool -tV y.o
y.o:
(__TEXT,__text) section
_t1:
0000000000000000 movl $_d1, %eax
% otool -rv y.o
y.o:
Relocation information (__TEXT,__text) 1 entries
address pcrel length extern type scattered symbolnum/value
00000001 False long False VANILLA False 2 (__DATA,__data)
So the change is based on it is not likely that an immediate Value
coming from an instruction field of a width of 1 byte, other than branches
and items with relocation, are not likely symbol addresses.
With the change the first case above simply becomes:
% otool -tV x.o
x.o:
(__TEXT,__text) section
_t1:
0000000000000000 vpshufd $0x0, %xmm1, %xmm0
and the second case continues to work as expected.
rdar://
14863405
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199698
91177308-0d34-0410-b5e6-
96231b3b80d8