From 31e90d2dd1986ed7933d992cfeb2c74fca8391c2 Mon Sep 17 00:00:00 2001
From: Torok Edwin <edwintorok@gmail.com>
Date: Wed, 4 Aug 2010 20:47:44 +0000
Subject: [PATCH] Use indirect calls in PowerPC JIT.

See PR5201. There is no way to know if direct calls will be within the allowed
range for BL. Hence emit all calls as indirect when in JIT mode.
Without this long-running applications will fail to JIT on PowerPC with a
relocation failure.

llvm-svn: 110246
---
 llvm/lib/Target/PowerPC/PPCISelLowering.cpp | 33 ++++++++++++++-------
 llvm/lib/Target/PowerPC/PPCSubtarget.cpp    |  4 +++
 llvm/lib/Target/PowerPC/PPCSubtarget.h      |  4 +++
 3 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 33d14412848a..14d1b154a5c9 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -2467,18 +2467,31 @@ unsigned PrepareCall(SelectionDAG &DAG, SDValue &Callee, SDValue &InFlag,
 
   unsigned CallOpc = isSVR4ABI ? PPCISD::CALL_SVR4 : PPCISD::CALL_Darwin;
 
-  // If the callee is a GlobalAddress/ExternalSymbol node (quite common, every
-  // direct call is) turn it into a TargetGlobalAddress/TargetExternalSymbol
-  // node so that legalize doesn't hack it.
-  if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee))
-    Callee = DAG.getTargetGlobalAddress(G->getGlobal(), dl, 
-                                        Callee.getValueType());
-  else if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(Callee))
-    Callee = DAG.getTargetExternalSymbol(S->getSymbol(), Callee.getValueType());
-  else if (SDNode *Dest = isBLACompatibleAddress(Callee, DAG))
+  bool needIndirectCall = true;
+  if (SDNode *Dest = isBLACompatibleAddress(Callee, DAG)) {
     // If this is an absolute destination address, use the munged value.
     Callee = SDValue(Dest, 0);
-  else {
+    needIndirectCall = false;
+  }
+  // XXX Work around for http://llvm.org/bugs/show_bug.cgi?id=5201
+  // Use indirect calls for ALL functions calls in JIT mode, since the
+  // far-call stubs may be outside relocation limits for a BL instruction.
+  if (!DAG.getTarget().getSubtarget<PPCSubtarget>().isJITCodeModel()) {
+    // If the callee is a GlobalAddress/ExternalSymbol node (quite common, every
+    // direct call is) turn it into a TargetGlobalAddress/TargetExternalSymbol
+    // node so that legalize doesn't hack it.
+    if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
+      Callee = DAG.getTargetGlobalAddress(G->getGlobal(), dl,
+					  Callee.getValueType());
+      needIndirectCall = false;
+    }
+  }
+  if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(Callee)) {
+      Callee = DAG.getTargetExternalSymbol(S->getSymbol(),
+					   Callee.getValueType());
+      needIndirectCall = false;
+  }
+  if (needIndirectCall) {
     // Otherwise, this is an indirect call.  We have to use a MTCTR/BCTRL pair
     // to do the call, we can't use PPCISD::CALL.
     SDValue MTCTROps[] = {Chain, Callee, InFlag};
diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
index 40914ba62a70..5d46065d96f2 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
@@ -69,6 +69,7 @@ PPCSubtarget::PPCSubtarget(const std::string &TT, const std::string &FS,
   , HasFSQRT(false)
   , HasSTFIWX(false)
   , HasLazyResolverStubs(false)
+  , IsJITCodeModel(false)
   , DarwinVers(0) {
 
   // Determine default and user specified characteristics
@@ -117,6 +118,9 @@ void PPCSubtarget::SetJITMode() {
   // everything is.  This matters for PPC64, which codegens in PIC mode without
   // stubs.
   HasLazyResolverStubs = false;
+
+  // Calls to external functions need to use indirect calls
+  IsJITCodeModel = true;
 }
 
 
diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.h b/llvm/lib/Target/PowerPC/PPCSubtarget.h
index 75fcf6238a27..00ec7474c9e3 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.h
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.h
@@ -63,6 +63,7 @@ protected:
   bool HasFSQRT;
   bool HasSTFIWX;
   bool HasLazyResolverStubs;
+  bool IsJITCodeModel;
   
   /// DarwinVers - Nonzero if this is a darwin platform.  Otherwise, the numeric
   /// version of the platform, e.g. 8 = 10.4 (Tiger), 9 = 10.5 (Leopard), etc.
@@ -124,6 +125,9 @@ public:
   bool hasLazyResolverStub(const GlobalValue *GV, 
                            const TargetMachine &TM) const;
   
+  // isJITCodeModel - True if we're generating code for the JIT
+  bool isJITCodeModel() const { return IsJITCodeModel; }
+
   // Specific obvious features.
   bool hasFSQRT() const { return HasFSQRT; }
   bool hasSTFIWX() const { return HasSTFIWX; }