[Autobackout][FuncReg]Revert of change: b9b2e02

Don't write the FP to stack for leaf functions, saves an extra store.

Author: dlei6g

IGC/Compiler/CISACodeGen/EmitVISAPass.cpp

@@ -10064,7 +10064,7 @@ void EmitPass::InitializeKernelStack(Function* pKernel)
     emitAddPointer(pSP, pStackBufferBase, pThreadOffset);
 
     // Push a new stack frame
-    emitPushFrameToStack(totalAllocaSize, pKernel);
+    emitPushFrameToStack(totalAllocaSize);
 
     // Set the total alloca size for the entry function
     m_encoder->SetFunctionAllocaStackSize(pKernel, totalAllocaSize);
@@ -10476,7 +10476,7 @@ void EmitPass::emitStackFuncEntry(Function* F)
     m_currShader->SaveStackState();
 
     // Push a new stack frame
-    emitPushFrameToStack(totalAllocaSize, F);
+    emitPushFrameToStack(totalAllocaSize);
 
     // Set the per-function private mem size
     m_encoder->SetFunctionAllocaStackSize(F, totalAllocaSize);
@@ -16362,22 +16362,16 @@ void EmitPass::emitGenISACopy(GenIntrinsicInst* GenCopyInst)
 //  Update FP to the current SP
 //  Increment SP by pushSize
 //  Store value of previous frame's FP to the address of updated FP (for stack-walk)
-void EmitPass::emitPushFrameToStack(unsigned& pushSize, Function* F)
+void EmitPass::emitPushFrameToStack(unsigned& pushSize)
 {
     CVariable* pFP = m_currShader->GetFP();
     CVariable* pSP = m_currShader->GetSP();
-    bool WriteOldFPToStack = IGC_IS_FLAG_ENABLED(EnableWriteOldFPToStack);
-    if (m_FGA && m_FGA->isLeafFunc(F))
-    {
-        // We don't need to do this if the function is already a leaf
-        WriteOldFPToStack = false;
-    }
 
     // Set FP = SP
     m_encoder->Copy(pFP, pSP);
     m_encoder->Push();
 
-    if (WriteOldFPToStack)
+    if IGC_IS_FLAG_ENABLED(EnableWriteOldFPToStack)
     {
         // Allocate 1 extra oword to store previous frame's FP
         pushSize += SIZE_OWORD;
@@ -16386,7 +16380,7 @@ void EmitPass::emitPushFrameToStack(unsigned& pushSize, Function* F)
     // Update SP by pushSize
     emitAddPointer(pSP, pSP, m_currShader->ImmToVariable(pushSize, ISA_TYPE_UD));
 
-    if (WriteOldFPToStack)
+    if IGC_IS_FLAG_ENABLED(EnableWriteOldFPToStack)
     {
         // Store old FP value to current FP
         CVariable* pOldFP = m_currShader->GetPrevFP();

IGC/Compiler/CISACodeGen/EmitVISAPass.hpp

@@ -426,7 +426,7 @@ class EmitPass : public llvm::FunctionPass
         uint32_t DstSubRegOffset = 0, uint32_t SrcSubRegOffset = 0);
     void emitCopyAll(CVariable* Dst, CVariable* Src, llvm::Type* Ty);
 
-    void emitPushFrameToStack(unsigned& pushSize, llvm::Function* F);
+    void emitPushFrameToStack(unsigned& pushSize);
     void emitAddPointer(CVariable* Dst, CVariable* Src, CVariable* offset);
     // emitAddPair - emulate 64bit addtition by 32-bit operations.
     // Dst and Src0 must be a 64-bit type variable.