Avoid unneeded frame entering/leaving when there's no slots to release. (#2854)

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/CodeGenerator.kt

@@ -8,7 +8,6 @@ package org.jetbrains.kotlin.backend.konan.llvm
 
 import kotlinx.cinterop.*
 import llvm.*
-import org.jetbrains.kotlin.backend.common.serialization.KotlinMangler
 import org.jetbrains.kotlin.backend.konan.*
 import org.jetbrains.kotlin.backend.konan.descriptors.isInterface
 import org.jetbrains.kotlin.backend.konan.llvm.objc.*
@@ -875,7 +874,6 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
 
     private fun position() = basicBlockToLastLocation[currentBlock]
 
-
     internal fun mapParameterForDebug(index: Int, value: LLVMValueRef) {
         appendingTo(localsInitBb) {
             LLVMBuildStore(builder, value, vars.addressOf(index))
@@ -897,7 +895,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
 
     internal fun epilogue() {
         appendingTo(prologueBb) {
-            val slots = if (needSlots)
+            val slots = if (needSlotsPhi)
                 LLVMBuildArrayAlloca(builder, kObjHeaderPtr, Int32(slotCount).llvm, "")!!
             else
                 kNullObjHeaderPtrPtr
@@ -909,7 +907,7 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
                                 Int32(slotCount * codegen.runtime.pointerSize).llvm,
                                 Int32(codegen.runtime.pointerAlignment).llvm,
                                 Int1(0).llvm))
-                call(context.llvm.enterFrameFunction, listOf(slots, Int32(vars.skip).llvm, Int32(slotCount).llvm))
+                call(context.llvm.enterFrameFunction, listOf(slots, Int32(vars.skipSlots).llvm, Int32(slotCount).llvm))
             }
             addPhiIncoming(slotsPhi!!, prologueBb to slots)
             memScoped {
@@ -1096,14 +1094,20 @@ internal class FunctionGenerationContext(val function: LLVMValueRef,
     }
 
     private val needSlots: Boolean
+        get() {
+            return slotCount - vars.skipSlots > frameOverlaySlotCount
+        }
+
+    private val needSlotsPhi: Boolean
         get() {
             return slotCount > frameOverlaySlotCount || localAllocs > 0
         }
 
+
     private fun releaseVars() {
         if (needSlots) {
             call(context.llvm.leaveFrameFunction,
-                    listOf(slotsPhi!!, Int32(vars.skip).llvm, Int32(slotCount).llvm))
+                    listOf(slotsPhi!!, Int32(vars.skipSlots).llvm, Int32(slotCount).llvm))
         }
     }
 }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt

@@ -562,11 +562,9 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
             if (function != null) {
                 parameters.forEach{
                     val parameter = it.key
-
-                    val local = functionGenerationContext.vars.createParameter(parameter,
-                            debugInfoIfNeeded(function, parameter))
+                    val local = functionGenerationContext.vars.createParameter(
+                            parameter, debugInfoIfNeeded(function, parameter))
                     functionGenerationContext.mapParameterForDebug(local, it.value)
-
                 }
             }
         }
@@ -586,7 +584,6 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
      */
     private inner class FunctionScope(val declaration: IrFunction?, val functionGenerationContext: FunctionGenerationContext) : InnerScopeImpl() {
 
-
         constructor(llvmFunction:LLVMValueRef, name:String, functionGenerationContext: FunctionGenerationContext):
                 this(null, functionGenerationContext) {
             this.llvmFunction = llvmFunction
@@ -597,7 +594,6 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
             codegen.llvmFunction(it)
         }
 
-
         val coverageInstrumentation: LLVMCoverageInstrumentation? =
                 context.coverage.tryGetInstrumentation(declaration) { function, args -> functionGenerationContext.call(function, args) }
 

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/VariableManager.kt

@@ -48,6 +48,7 @@ internal class VariableManager(val functionGenerationContext: FunctionGeneration
 
     // Clears inner state of variable manager.
     fun clear() {
+        skipSlots = 0
         variables.clear()
         contextVariablesToIndex.clear()
     }
@@ -78,17 +79,18 @@ internal class VariableManager(val functionGenerationContext: FunctionGeneration
         return index
     }
 
-    internal var skip = 0
+    internal var skipSlots = 0
     internal fun createParameter(valueDeclaration: IrValueDeclaration, variableLocation: VariableDebugLocation?) : Int {
         assert(!contextVariablesToIndex.contains(valueDeclaration))
         val index = variables.size
         val type = functionGenerationContext.getLLVMType(valueDeclaration.type)
-        val slot = functionGenerationContext.alloca(type, "p-${valueDeclaration.name.asString()}", variableLocation)
+        val slot = functionGenerationContext.alloca(
+                type, "p-${valueDeclaration.name.asString()}", variableLocation)
         val isObject = functionGenerationContext.isObjectType(type)
         variables.add(ParameterRecord(slot, isObject))
         contextVariablesToIndex[valueDeclaration] = index
         if (isObject)
-            skip++
+            skipSlots++
         return index
     }