Producers / Consumers Analysis

ASM has a built-in `SourceValue` analysis which computes for each
value a set of instructions that may possibly have constructed it.

The ProdConsAnalyzer class provides additional queries over the
result of the SourceValue analysis:
  - consumers of values
  - tracking producers / consumers through copying operations (load,
    store, etc)

A fix to (and therefore a new version of) ASM was required. See here:
scala/scala-asm@94106a5472

Author: lrytz

src/compiler/scala/tools/nsc/backend/jvm/analysis/InstructionStackEffect.scala

@@ -94,7 +94,7 @@ object InstructionStackEffect {
         val isSize2 = peekStack(0).getSize == 2
         if (isSize2) t(1, 0) else t(2, 0)
 
-      case DUP => t(0, 1)
+      case DUP => t(1, 2)
 
       case DUP_X1 => t(2, 3)
 
@@ -104,7 +104,7 @@ object InstructionStackEffect {
 
       case DUP2 =>
         val isSize2 = peekStack(0).getSize == 2
-        if (isSize2) t(0, 1) else t(0, 2)
+        if (isSize2) t(1, 2) else t(2, 4)
 
       case DUP2_X1 =>
         val isSize2 = peekStack(0).getSize == 2