[PowerPC] Use the ABI indirect-call protocol for patchpoints

We used to take the address specified as the direct target of the patchpoint
and did no TOC-pointer handling.  This, however, as not all that useful,
because MCJIT tends to create a lot of modules, and they have their own TOC
sections. Thus, to call from the generated code to other generated code, you
really need to switch TOC pointers. Make this work as expected, and under
ELFv1, tread the address as the function descriptor address so that the correct
TOC pointer can be loaded.

llvm-svn: 242217

1 files changed, 43 insertions, 1 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
index adcf8ee8291..199a0debf88 100644
--- a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -369,28 +369,70 @@ void PPCAsmPrinter::LowerPATCHPOINT(MCStreamer &OutStreamer, StackMaps &SM,
     assert((CallTarget & 0xFFFFFFFFFFFF) == CallTarget &&
            "High 16 bits of call target should be zero.");
     unsigned ScratchReg = MI.getOperand(Opers.getNextScratchIdx()).getReg();
-    EncodedBytes = 6*4;
+    EncodedBytes = 0;
     // Materialize the jump address:
     EmitToStreamer(OutStreamer, MCInstBuilder(PPC::LI8)
                                     .addReg(ScratchReg)
                                     .addImm((CallTarget >> 32) & 0xFFFF));
+    ++EncodedBytes;
     EmitToStreamer(OutStreamer, MCInstBuilder(PPC::RLDIC)
                                     .addReg(ScratchReg)
                                     .addReg(ScratchReg)
                                     .addImm(32).addImm(16));
+    ++EncodedBytes;
     EmitToStreamer(OutStreamer, MCInstBuilder(PPC::ORIS8)
                                     .addReg(ScratchReg)
                                     .addReg(ScratchReg)
                                     .addImm((CallTarget >> 16) & 0xFFFF));
+    ++EncodedBytes;
     EmitToStreamer(OutStreamer, MCInstBuilder(PPC::ORI8)
                                     .addReg(ScratchReg)
                                     .addReg(ScratchReg)
                                     .addImm(CallTarget & 0xFFFF));
 
+    // Save the current TOC pointer before the remote call.
+    int TOCSaveOffset = Subtarget->isELFv2ABI() ? 24 : 40;
+    EmitToStreamer(OutStreamer, MCInstBuilder(PPC::STD)
+                                    .addReg(PPC::X2)
+                                    .addImm(TOCSaveOffset)
+                                    .addReg(PPC::X1));
+    ++EncodedBytes;
+
+
+    // If we're on ELFv1, then we need to load the actual function pointer from
+    // the function descriptor.
+    if (!Subtarget->isELFv2ABI()) {
+      // Load the new TOC pointer and the function address, but not r11
+      // (needing this is rare, and loading it here would prevent passing it
+      // via a 'nest' parameter.
+      EmitToStreamer(OutStreamer, MCInstBuilder(PPC::LD)
+                                      .addReg(PPC::X2)
+                                      .addImm(8)
+                                      .addReg(ScratchReg));
+      ++EncodedBytes;
+      EmitToStreamer(OutStreamer, MCInstBuilder(PPC::LD)
+                                      .addReg(ScratchReg)
+                                      .addImm(0)
+                                      .addReg(ScratchReg));
+      ++EncodedBytes;
+    }
+
     EmitToStreamer(OutStreamer, MCInstBuilder(PPC::MTCTR8).addReg(ScratchReg));
+    ++EncodedBytes;
     EmitToStreamer(OutStreamer, MCInstBuilder(PPC::BCTRL8));
+    ++EncodedBytes;
+
+    // Restore the TOC pointer after the call.
+    EmitToStreamer(OutStreamer, MCInstBuilder(PPC::LD)
+                                    .addReg(PPC::X2)
+                                    .addImm(TOCSaveOffset)
+                                    .addReg(PPC::X1));
+    ++EncodedBytes;
   }
 
+  // Each instruction is 4 bytes.
+  EncodedBytes *= 4;
+
   // Emit padding.
   unsigned NumBytes = Opers.getMetaOper(PatchPointOpers::NBytesPos).getImm();
   assert(NumBytes >= EncodedBytes &&