[Autobackout][FuncReg]Revert of change: e2d4d33

 remove dead instructions with debug info enabled.

This change removes IGC backend pattern match dependency setting on arguments to debug instructions.
  call void @llvm.dbg.value(metadata float %8, metadata !903, metadata !DIExpression()), !dbg !901		; visa id: 20
This forces generation of instruction producing %8.  However, if that instruction is not used, it will be generated in dead code.
For example,
  %8 = load float, float addrspace(1)* %7, align 4, !dbg !902		; visa id: 18
  ...
  %simdShuffle = call float @llvm.genx.GenISA.WaveShuffleIndex.f32(float %8, i32 0, i32 0), !dbg !981		; visa id: 23
  ...
  call void @llvm.dbg.value(metadata float %simdShuffle, metadata !904, metadata !DIExpression()), !dbg !901		; visa id: 26
  ...
  %9 = fadd fast float %simdShuffle, %simdShuffle.1, !dbg !982		; visa id: 30
The pattern matcher will link out %simdShuffle and directly use %8 (regioning),
However, llvm.dbg.value creates a false dependency on %simdShuffle and causes the shuffle
to emit a dead broadcast mov in vISA.

This change wouldn't impact in -O0 debug mode, and just impact -O2 debug mode.

Author: trbauer

IGC/Compiler/CISACodeGen/PatternMatchPass.cpp

@@ -1515,7 +1515,7 @@ namespace IGC
 
     void CodeGenPatternMatch::visitDbgInfoIntrinsic(DbgInfoIntrinsic& I)
     {
-        // Nothing to do
+        MatchDbgInstruction(I);
     }
 
     void CodeGenPatternMatch::visitInsertValueInst(InsertValueInst& I)
@@ -4970,6 +4970,38 @@ namespace IGC
         return MatchSingleInstruction(I);
     }
 
+    bool CodeGenPatternMatch::MatchDbgInstruction(llvm::DbgInfoIntrinsic& I)
+    {
+        struct DbgInstPattern : Pattern
+        {
+            virtual void Emit(EmitPass* pass, const DstModifier& modifier)
+            {
+                // Nothing to emit.
+            }
+        };
+        DbgInstPattern* pattern = new (m_allocator) DbgInstPattern();
+        if (DbgDeclareInst * pDbgDeclInst = dyn_cast<DbgDeclareInst>(&I))
+        {
+            if (pDbgDeclInst->getAddress())
+            {
+                MarkAsSource(pDbgDeclInst->getAddress());
+            }
+        }
+        else if (DbgValueInst * pDbgValInst = dyn_cast<DbgValueInst>(&I))
+        {
+            if (pDbgValInst->getValue())
+            {
+                MarkAsSource(pDbgValInst->getValue());
+            }
+        }
+        else
+        {
+            IGC_ASSERT_MESSAGE(0, "Unhandled Dbg intrinsic");
+        }
+        AddPattern(pattern);
+        return true;
+    }
+
     bool CodeGenPatternMatch::MatchAvg(llvm::Instruction& I)
     {
         // "Average value" pattern:

IGC/Compiler/CISACodeGen/PatternMatchPass.hpp

@@ -224,6 +224,7 @@ namespace IGC
         bool MatchBlockReadWritePointer(llvm::GenIntrinsicInst& I);
         bool MatchGradient(llvm::GenIntrinsicInst& I);
         bool MatchSampleDerivative(llvm::GenIntrinsicInst& I);
+        bool MatchDbgInstruction(llvm::DbgInfoIntrinsic& I);
         bool MatchAvg(llvm::Instruction& I);
 
         bool MatchMinMax(llvm::SelectInst& I);