[PowerPC] Do not use BLA with the 64-bit SVR4 ABI

The PowerPC back-end uses BLA to implement calls to functions at
known-constant addresses, which is apparently used for certain
system routines on Darwin.

However, with the 64-bit SVR4 ABI, this is actually incorrect.
An immediate function pointer value on this platform is not
directly usable as a target address for BLA:
- in the ELFv1 ABI, the function pointer value refers to the
  *function descriptor*, not the code address
- in the ELFv2 ABI, the function pointer value refers to the
  global entry point, but BL(A) would only be correct when
  calling the *local* entry point

This bug didn't show up since using immediate function pointer
values is not usually done in the 64-bit SVR4 ABI in the first
place.  However, I ran into this issue with a certain use case
of LLVM as JIT, where immediate function pointer values were
uses to implement callbacks from JITted code to helpers in
statically compiled code.

Fixed by simply not using BLA with the 64-bit SVR4 ABI.

llvm-svn: 211174

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

@@ -3431,11 +3431,12 @@ unsigned PrepareCall(SelectionDAG &DAG, SDValue &Callee, SDValue &InFlag,
   unsigned CallOpc = PPCISD::CALL;
 
   bool needIndirectCall = true;
-  if (SDNode *Dest = isBLACompatibleAddress(Callee, DAG)) {
-    // If this is an absolute destination address, use the munged value.
-    Callee = SDValue(Dest, 0);
-    needIndirectCall = false;
-  }
+  if (!isSVR4ABI || !isPPC64)
+    if (SDNode *Dest = isBLACompatibleAddress(Callee, DAG)) {
+      // If this is an absolute destination address, use the munged value.
+      Callee = SDValue(Dest, 0);
+      needIndirectCall = false;
+    }
 
   if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
     // XXX Work around for http://llvm.org/bugs/show_bug.cgi?id=5201
@@ -4383,8 +4384,7 @@ PPCTargetLowering::LowerCall_64SVR4(SDValue Chain, SDValue Callee,
   // pointers in the 64-bit SVR4 ABI.
   if (!isTailCall &&
       !dyn_cast<GlobalAddressSDNode>(Callee) &&
-      !dyn_cast<ExternalSymbolSDNode>(Callee) &&
-      !isBLACompatibleAddress(Callee, DAG)) {
+      !dyn_cast<ExternalSymbolSDNode>(Callee)) {
     // Load r2 into a virtual register and store it to the TOC save area.
     SDValue Val = DAG.getCopyFromReg(Chain, dl, PPC::X2, MVT::i64);
     // TOC save area offset.

llvm/test/CodeGen/PowerPC/ppc64-calls.ll

@@ -42,15 +42,6 @@ define void @test_indirect(void ()* nocapture %fp) nounwind {
   ret void
 }
 
-; Absolute vales should be have the TOC restore 'nop'
-define void @test_abs() nounwind {
-; CHECK-LABEL: test_abs:
-  tail call void inttoptr (i64 1024 to void ()*)() nounwind
-; CHECK: bla 1024
-; CHECK-NEXT: nop
-  ret void
-}
-
 declare double @sin(double) nounwind
 
 ; External functions call should also have a 'nop'