[mips] Do not tail-call optimize vararg functions or functions with byval

arguments.

This is rather conservative and should be fixed later to be more aggressive.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166851 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 8 insertions, 9 deletions

diff --git a/lib/Target/Mips/MipsISelLowering.cpp b/lib/Target/Mips/MipsISelLowering.cpp
index 02674f5d05..94e18689b7 100644
--- a/lib/Target/Mips/MipsISelLowering.cpp
+++ b/lib/Target/Mips/MipsISelLowering.cpp
@@ -2639,19 +2639,16 @@ static unsigned getNextIntArgReg(unsigned Reg) {
 /// IsEligibleForTailCallOptimization - Check whether the call is eligible
 /// for tail call optimization.
 bool MipsTargetLowering::
-IsEligibleForTailCallOptimization(CallingConv::ID CalleeCC,
+IsEligibleForTailCallOptimization(const MipsCC &MipsCCInfo, bool IsVarArg,
                                   unsigned NextStackOffset) const {
   if (!EnableMipsTailCalls)
     return false;
 
-  // Do not tail-call optimize if there is an argument passed on stack.
-  if (IsO32 && (CalleeCC != CallingConv::Fast)) {
-    if (NextStackOffset > 16)
-      return false;
-  } else if (NextStackOffset)
+  if (MipsCCInfo.hasByValArg() || IsVarArg)
     return false;
 
-  return true;
+  // Return true if no arguments are passed on stack.
+  return MipsCCInfo.reservedArgArea() == NextStackOffset;
 }
 
 /// LowerCall - functions arguments are copied from virtual regs to
@@ -2690,7 +2687,8 @@ MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
 
   // Check if it's really possible to do a tail call.
   if (isTailCall)
-    isTailCall = IsEligibleForTailCallOptimization(CallConv, NextStackOffset);
+    isTailCall = IsEligibleForTailCallOptimization(MipsCCInfo, isVarArg,
+                                                   NextStackOffset);
 
   if (isTailCall)
     ++NumTailCalls;
diff --git a/lib/Target/Mips/MipsISelLowering.h b/lib/Target/Mips/MipsISelLowering.h
index 160349e4aa..9e8c659829 100644
--- a/lib/Target/Mips/MipsISelLowering.h
+++ b/lib/Target/Mips/MipsISelLowering.h
@@ -274,7 +274,8 @@ namespace llvm {
 
     /// IsEligibleForTailCallOptimization - Check whether the call is eligible
     /// for tail call optimization.
-    bool IsEligibleForTailCallOptimization(CallingConv::ID CalleeCC,
+    bool IsEligibleForTailCallOptimization(const MipsCC &MipsCCInfo,
+                                           bool IsVarArg,
                                            unsigned NextStackOffset) const;
 
     /// copyByValArg - Copy argument registers which were used to pass a byval