Re-enable dst for lifetime_start in resourec loop header

Re-enable dst for lifetime_start in resourec loop header. Set the
condition to benefit compatible workloads.

Author: ichenkai

IGC/Compiler/CISACodeGen/EmitVISAPass.cpp

@@ -8776,8 +8776,7 @@ void EmitPass::emitGather4Instruction(SamplerGatherIntrinsic *inst) {
           : false;
   uint label = 0;
   CVariable *flag = nullptr;
-  CVariable *dest = dst ? dst : m_destination;
-  bool needLoop = ResourceLoopHeader(dest, resource, sampler, flag, label);
+  bool needLoop = ResourceLoopHeader(dst, resource, sampler, flag, label);
   ResourceLoopSubIteration(resource, sampler, flag, label);
   m_encoder->SetPredicate(flag);
   m_encoder->Gather4Inst(opCode, offset, resource, pairedResource, sampler,
@@ -15963,8 +15962,7 @@ void EmitPass::emitAtomicRaw(llvm::GenIntrinsicInst *pInst, Value *dstAddr,
       }
       uint label = 0;
       CVariable *flag = nullptr;
-      CVariable *dest = pDst ? pDst : m_destination;
-      bool needLoop = ResourceLoopHeader(dest, resource, flag, label);
+      bool needLoop = ResourceLoopHeader(pDst, resource, flag, label);
       ResourceLoopSubIteration(resource, flag, label);
       if (shouldGenerateLSC(pInst)) {
         auto cacheOpts = LSC_DEFAULT_CACHING;
@@ -21525,6 +21523,11 @@ bool EmitPass::ResourceLoopHeader(const CVariable *destination,
   }
   m_currShader->IncNumSampleBallotLoops();
 
+  auto *md = m_pCtx->getModuleMetaData();
+  if (destination && IGC_IS_FLAG_ENABLED(EnableResourceLoopDestLifeTimeStart) &&
+      !md->compOpt.DisableResourceLoopDestLifeTimeStart) {
+    m_encoder->Lifetime(LIFETIME_START, (CVariable *)destination);
+  }
 
   label = m_encoder->GetNewLabelID("_opt_resource_loop");
   m_encoder->AddDivergentResourceLoopLabel(label);

IGC/common/MDFrameWork.h

@@ -503,6 +503,7 @@ enum class ShaderTypeMD
         bool DisableLoopUnroll                          = false;
         unsigned ForcePushConstantMode                  = 0;
         bool UseInstructionHoistingOptimization         = false;
+        bool DisableResourceLoopDestLifeTimeStart = false;
     };
 
     enum class ThreadIDLayout

IGC/common/igc_flags.h

@@ -370,6 +370,9 @@ DECLARE_IGC_REGKEY(bool, DivRemIncrementCondBranchSimplify, false, "Create branc
 DECLARE_IGC_REGKEY(bool, EnableInstructionHoistingOptimization, false,
                    "Enable optimization for hoisting latency instructions",
                    false)
+DECLARE_IGC_REGKEY(bool, EnableResourceLoopDestLifeTimeStart, true,
+                   "Enable lifetime_start set for destination in resource loop",
+                   false)
 
 DECLARE_IGC_GROUP("Shader debugging")
 DECLARE_IGC_REGKEY(bool, CopyA0ToDBG0,                  false, " Copy a0 used for extended msg descriptor to dbg0 to help debug", false)