SI-6188 ICodeReader notes exception handlers, Inliner takes them into…

… account

src/compiler/scala/tools/nsc/backend/icode/Members.scala

@@ -170,6 +170,7 @@ trait Members {
     var sourceFile: SourceFile = NoSourceFile
     var returnType: TypeKind = _
     var recursive: Boolean = false
+    var bytecodeHasEHs = false // set by ICodeReader only, used by Inliner to prevent inlining (SI-6188)
 
     /** local variables and method parameters */
     var locals: List[Local] = Nil

src/compiler/scala/tools/nsc/backend/opt/Inliners.scala

@@ -405,6 +405,12 @@ abstract class Inliners extends SubComponent {
               val inc   = new IMethodInfo(callee)
               val pair  = new CallerCalleeInfo(caller, inc, fresh, inlinedMethodCount)
 
+              if(inc.hasHandlers && (stackLength == -1)) {
+                // no inlining is done, yet don't warn about it, stackLength == -1 indicates we're trying to inlineWithoutTFA.
+                // Shortly, a TFA will be computed and an error message reported if indeed inlining not possible.
+                return false
+              }
+
                (pair isStampedForInlining stackLength) match {
 
                  case inlInfo if inlInfo.isSafe =>
@@ -605,7 +611,7 @@ abstract class Inliners extends SubComponent {
       def isSmall       = (length <= SMALL_METHOD_SIZE) && blocks(0).length < 10
       def isLarge       = length > MAX_INLINE_SIZE
       def isRecursive   = m.recursive
-      def hasHandlers   = handlers.nonEmpty
+      def hasHandlers   = handlers.nonEmpty || m.bytecodeHasEHs
 
       def isSynchronized         = sym.hasFlag(Flags.SYNCHRONIZED)
       def hasNonFinalizerHandler = handlers exists {
@@ -941,6 +947,7 @@ abstract class Inliners extends SubComponent {
             if(inc.isRecursive)    { rs ::= "is recursive"           }
             if(isInlineForbidden)  { rs ::= "is annotated @noinline" }
             if(inc.isSynchronized) { rs ::= "is synchronized method" }
+            if(inc.m.bytecodeHasEHs) { rs ::= "bytecode contains exception handlers / finally clause" } // SI-6188
             if(rs.isEmpty) null else rs.mkString("", ", and ", "")
           }
 
@@ -974,6 +981,10 @@ abstract class Inliners extends SubComponent {
           return DontInlineHere("too low score (heuristics)")
         }
 
+        if(inc.hasHandlers && (stackLength != 0)) {
+          // TODO pending return DontInlineHere("callee contains exception handlers / finally clause, and is invoked with non-empty operand stack") // SI-6157
+        }
+
         if(isKnownToInlineSafely) { return InlineableAtThisCaller }
 
         if(stackLength > inc.minimumStack && inc.hasNonFinalizerHandler) {

src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala

@@ -594,6 +594,7 @@ abstract class ICodeReader extends ClassfileParser {
     while (pc < codeLength) parseInstruction
 
     val exceptionEntries = in.nextChar.toInt
+    code.containsEHs = (exceptionEntries != 0)
     var i = 0
     while (i < exceptionEntries) {
       // skip start end PC
@@ -647,6 +648,7 @@ abstract class ICodeReader extends ClassfileParser {
 
     var containsDUPX = false
     var containsNEW  = false
+    var containsEHs  = false
 
     def emit(i: Instruction) {
       instrs += ((pc, i))
@@ -664,6 +666,7 @@ abstract class ICodeReader extends ClassfileParser {
 
       val code = new Code(method)
       method.setCode(code)
+      method.bytecodeHasEHs = containsEHs
       var bb = code.startBlock
 
       def makeBasicBlocks: mutable.Map[Int, BasicBlock] =

test/files/run/t6188.check

@@ -0,0 +1 @@
+Failure(java.lang.Exception: this is an exception)

test/files/run/t6188.flags

@@ -0,0 +1 @@
+ -optimize 

test/files/run/t6188.scala

@@ -0,0 +1,12 @@
+// SI-6188 Optimizer incorrectly removes method invocations containing throw expressions
+
+import scala.util.Success
+
+object Test {
+ def main(args: Array[String]) {
+   val e = new Exception("this is an exception")
+   val res = Success(1).flatMap[Int](x => throw e)
+   println(res)
+ }
+}
+