Make X86-64 in the Large model always emit 64-bit calls.

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!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@88984 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 17 deletions

diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index a85e11e..5f195ee 100644
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -247,16 +247,6 @@ namespace {
     /// specified GV address.
     void *getGlobalValueIndirectSym(GlobalValue *V, void *GVAddress);
 
-    /// AddCallbackAtLocation - If the target is capable of rewriting an
-    /// instruction without the use of a stub, record the location of the use so
-    /// we know which function is being used at the location.
-    void *AddCallbackAtLocation(Function *F, void *Location) {
-      MutexGuard locked(TheJIT->lock);
-      /// Get the target-specific JIT resolver function.
-      state.AddCallSite(locked, Location, F);
-      return (void*)(intptr_t)LazyResolverFn;
-    }
-
     void getRelocatableGVs(SmallVectorImpl<GlobalValue*> &GVs,
                            SmallVectorImpl<void*> &Ptrs);
 
@@ -756,13 +746,6 @@ void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
       !MayNeedFarStub)
     return TheJIT->getPointerToFunction(F);
 
-  // Okay, the function has not been compiled yet, if the target callback
-  // mechanism is capable of rewriting the instruction directly, prefer to do
-  // that instead of emitting a stub.  This uses the lazy resolver, so is not
-  // legal if lazy compilation is disabled.
-  if (!MayNeedFarStub && TheJIT->isCompilingLazily())
-    return Resolver.AddCallbackAtLocation(F, Reference);
-
   // Otherwise, we have to emit a stub.
   void *StubAddr = Resolver.getFunctionStub(F);