Last round of changes for ARM tail calls.

Not turning them on yet.

llvm-svn: 106295

2 files changed, 16 insertions, 9 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 5ec995f771c..50258c6f85e 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -1101,7 +1101,7 @@ ARMTargetLowering::LowerCall(SDValue Chain, SDValue Callee,
       }
     } else if (VA.isRegLoc()) {
       RegsToPass.push_back(std::make_pair(VA.getLocReg(), Arg));
-    } else {
+    } else if (!IsSibCall) {
       assert(VA.isMemLoc());
 
       MemOpChains.push_back(LowerMemOpCallTo(Chain, StackPtr, Arg,
@@ -1357,12 +1357,6 @@ ARMTargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
   // Look for obvious safe cases to perform tail call optimization that do not
   // require ABI changes. This is what gcc calls sibcall.
 
-  // Can't do sibcall if stack needs to be dynamically re-aligned. PEI needs to
-  // emit a special epilogue.
-  // Not sure yet if this is true on ARM.
-//??  if (RegInfo->needsStackRealignment(MF))
-//??    return false;
-
   // Do not sibcall optimize vararg calls unless the call site is not passing
   // any arguments.
   if (isVarArg && !Outs.empty())
@@ -1373,6 +1367,19 @@ ARMTargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
   if (isCalleeStructRet || isCallerStructRet)
     return false;
 
+  // On Thumb, for the moment, we can only do this to functions defined in this
+  // compilation, or to indirect calls.  A Thumb B to an ARM function is not
+  // easily fixed up in the linker, unlike BL.
+  if (Subtarget->isThumb()) {
+    if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
+      const GlobalValue *GV = G->getGlobal();
+      if (GV->isDeclaration() || GV->isWeakForLinker())
+        return false;
+    } else if (isa<ExternalSymbolSDNode>(Callee)) {
+      return false;
+    }
+  }
+
   // If the calling conventions do not match, then we'd better make sure the
   // results are returned in the same way as what the caller expects.
   if (!CCMatch) {
diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 052104d0533..d95137ae900 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -1049,7 +1049,7 @@ let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1 in {
                      "@TC_RETURN","\t$dst", []>, Requires<[IsDarwin]>;
 
   def TAILJMPd : ABXI<0b1010, (outs), (ins brtarget:$dst, variable_ops),
-                 IIC_Br, "b\t$dst  @ TAILCALL",
+                 IIC_Br, "b.w\t$dst  @ TAILCALL",
                  []>, Requires<[IsDarwin]>;
 
   def TAILJMPr : AXI<(outs), (ins tcGPR:$dst, variable_ops),
@@ -1084,7 +1084,7 @@ let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1 in {
                      "@TC_RETURN","\t$dst", []>, Requires<[IsNotDarwin]>;
 
   def TAILJMPdND : ABXI<0b1010, (outs), (ins brtarget:$dst, variable_ops),
-                 IIC_Br, "b\t$dst  @ TAILCALL",
+                 IIC_Br, "b.w\t$dst  @ TAILCALL",
                  []>, Requires<[IsNotDarwin]>;
 
   def TAILJMPrND : AXI<(outs), (ins tGPR:$dst, variable_ops),