The large code model is documented at
http://www.x86-64.org/documentation/abi.pdf and says that calls should
assume their target doesn't live within the 32-bit pc-relative offset
that fits in the call instruction.
To do this, we turn off the global-address->target-global-address
conversion in X86TargetLowering::LowerCall(). The first attempt at
this broke the lazy JIT because it can separate the movabs(imm->reg)
from the actual call instruction. The lazy JIT receives the address of
the movabs as a relocation and needs to record the return address from
the call; and then when that call happens, it needs to patch the
movabs with the newly-compiled target. We could thread the call
instruction into the relocation and record the movabs<->call mapping
explicitly, but that seems to require at least as much new
complication in the code generator as this change.
To fix this, we make lazy functions _always_ go through a call
stub. You'd think we'd only have to force lazy calls through a stub on
difficult platforms, but that turns out to break indirect calls
through a function pointer. The right fix for that is to distinguish
between calls and address-of operations on uncompiled functions, but
that's complex enough to leave for someone else to do.
Another attempt at this defined a new CALL64i pseudo-instruction,
which expanded to a 2-instruction sequence in the assembly output and
was special-cased in the X86CodeEmitter's emitInstruction()
function. That broke indirect calls in the same way as above.
This patch also removes a hack forcing Darwin to the small code model.
Without far-call-stubs, the small code model requires things of the
JITMemoryManager that the DefaultJITMemoryManager can't provide.
Thanks to echristo for lots of testing!
llvm-svn: 88984
- This is an initial step towards -march=native support in Clang, and towards
eliminating host dependencies in the targets. See PR5389.
- Patch by Roman Divacky!
llvm-svn: 88768
Provide special isLoadFromStackSlotPostFE and isStoreToStackSlotPostFE
interfaces to explicitly request checking for post-frame ptr elimination
operands. This uses a heuristic so it isn't reliable for correctness.
llvm-svn: 87047
machine instruction loads or stores from/to a stack slot. Unlike
isLoadFromStackSlot and isStoreFromStackSlot, the instruction may be
something other than a pure load/store (e.g. it may be an arithmetic
operation with a memory operand). This helps AsmPrinter determine when
to print a spill/reload comment.
This is only a hint since we may not be able to figure this out in all
cases. As such, it should not be relied upon for correctness.
Implement for X86. Return false by default for other architectures.
llvm-svn: 87026
slots. The AsmPrinter will use this information to determine whether to
print a spill/reload comment.
Remove default argument values. It's too easy to pass a wrong argument
value when multiple arguments have default values. Make everything
explicit to trap bugs early.
Update all targets to adhere to the new interfaces..
llvm-svn: 87022
can only branch forward. To best take advantage of them, we'd like to adjust
the basic blocks around a bit when reasonable. This patch puts basics in place
to do that, with a super-simple algorithm for backwards jump table targets that
creates a new branch after the jump table which branches backwards. Real
heuristics for reordering blocks or other modifications rather than inserting
branches will follow.
llvm-svn: 86791
