[X86] Make the instructions that use AdSize16/32/64 co-exist together without using...

[oota-llvm.git] / lib / Target / X86 / X86FrameLowering.cpp

diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index c408fddf89094f39292bb20d468ec22ab00c68ee..95bca7d936f69dc98cf2543a584fe23d6ca53d85 100644 (file)
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/lib/Target/X86/X86FrameLowering.cpp
@@ -1648,12 +1648,36 @@ X86FrameLowering::adjustForSegmentedStacks(MachineFunction &MF) const {
   }
 
   // __morestack is in libgcc
-  if (Is64Bit)
-    BuildMI(allocMBB, DL, TII.get(X86::CALL64pcrel32))
-      .addExternalSymbol("__morestack");
-  else
-    BuildMI(allocMBB, DL, TII.get(X86::CALLpcrel32))
-      .addExternalSymbol("__morestack");
+  if (Is64Bit && MF.getTarget().getCodeModel() == CodeModel::Large) {
+    // Under the large code model, we cannot assume that __morestack lives
+    // within 2^31 bytes of the call site, so we cannot use pc-relative
+    // addressing. We cannot perform the call via a temporary register,
+    // as the rax register may be used to store the static chain, and all
+    // other suitable registers may be either callee-save or used for
+    // parameter passing. We cannot use the stack at this point either
+    // because __morestack manipulates the stack directly.
+    //
+    // To avoid these issues, perform an indirect call via a read-only memory
+    // location containing the address.
+    //
+    // This solution is not perfect, as it assumes that the .rodata section
+    // is laid out within 2^31 bytes of each function body, but this seems
+    // to be sufficient for JIT.
+    BuildMI(allocMBB, DL, TII.get(X86::CALL64m))
+        .addReg(X86::RIP)
+        .addImm(0)
+        .addReg(0)
+        .addExternalSymbol("__morestack_addr")
+        .addReg(0);
+    MF.getMMI().setUsesMorestackAddr(true);
+  } else {
+    if (Is64Bit)
+      BuildMI(allocMBB, DL, TII.get(X86::CALL64pcrel32))
+        .addExternalSymbol("__morestack");
+    else
+      BuildMI(allocMBB, DL, TII.get(X86::CALLpcrel32))
+        .addExternalSymbol("__morestack");
+  }
 
   if (IsNested)
     BuildMI(allocMBB, DL, TII.get(X86::MORESTACK_RET_RESTORE_R10));