Fix instruction index bugs.

Index increments were being missed due to them being passed by value and
not reference! This led to the IR using incorrect local variable
operands in some cases.

Tests will be added (where possible) to Yk's IR lowering suite.

Author: vext01

llvm/lib/YkIR/YkIRWriter.cpp

@@ -239,7 +239,7 @@ class YkIRWriter {
   }
 
   void serialiseAllocaInst(AllocaInst *I, ValueLoweringMap &VLMap,
-                           unsigned BBIdx, unsigned InstIdx) {
+                           unsigned BBIdx, unsigned &InstIdx) {
     // type_index:
     OutStreamer.emitSizeT(typeIndex(I->getType()));
     // opcode:
@@ -265,7 +265,7 @@ class YkIRWriter {
   }
 
   void serialiseCallInst(CallInst *I, ValueLoweringMap &VLMap, unsigned BBIdx,
-                         unsigned InstIdx) {
+                         unsigned &InstIdx) {
     // type_index:
     OutStreamer.emitSizeT(typeIndex(I->getType()));
     // opcode:
@@ -289,7 +289,7 @@ class YkIRWriter {
   }
 
   void serialiseBranchInst(BranchInst *I, ValueLoweringMap &VLMap,
-                           unsigned BBIdx, unsigned InstIdx) {
+                           unsigned BBIdx, unsigned &InstIdx) {
     // We split LLVM's `br` into two Yk IR instructions: one for unconditional
     // branching, another for conidtional branching.
     if (!I->isConditional()) {