Add Induction Variable Elimination pass.

This pass, also referred as IndVarSimplify pass, is generic LLVM pass.
When added to OptimizeIR() function, it improves performance
for cases like in this pseudo code:
    uint max = data[thread_invocation_id];
    for(uint i = 0; i < max; ++i)
    {
        n += 321;
    }
With this pass the code can be transformed to just:
    n += 321 * data[thread_invocation_id];

Change-Id: Ie536a5d487bdc4b15f648454a653dfe030eb7764

Author: MaciejKalinski

IGC/Compiler/CISACodeGen/ShaderCodeGen.cpp

@@ -1439,6 +1439,7 @@ namespace IGC
                 // disable loop unroll for excessive large shaders
                 if (pContext->m_instrTypes.hasLoop)
                 {
+                    mpm.add(createIndVarSimplifyPass());
                     mpm.add(createLoopDeadCodeEliminationPass());
                     mpm.add(createLoopCanonicalization());
                     mpm.add(llvm::createLoopDeletionPass());