[Autobackout][FuncReg]Revert of change: 763ce29

Now appropriately handling shl instructions with unsupported types.

Fixing and adding more use cases for cleanupTruncInst including cases where we have chained trunc instructions or when a trunc is followed by a zext/sext. All cases verified by Alive tool

Author: paigeale

IGC/Compiler/Legalizer/PeepholeTypeLegalizer.cpp

@@ -461,11 +461,6 @@ void PeepholeTypeLegalizer::legalizeBinaryOperator(Instruction& I) {
             NewLargeRes = m_builder->CreateAShr(NewLargeSrc1, NewLargeSrc2);
             break;
         }
-        case Instruction::Shl:
-        {
-            NewLargeRes = m_builder->CreateShl(NewLargeSrc1, NewLargeSrc2);
-            break;
-        }
         default:
             printf("Binary Instruction seen with illegal int type. Legalization support missing. Inst opcode:%d", I.getOpcode());
             IGC_ASSERT_MESSAGE(0, "Binary Instruction seen with illegal int type. Legalization support missing.");
@@ -900,59 +895,20 @@ void PeepholeTypeLegalizer::cleanupTruncInst(Instruction& I) {
         I.hasOneUse() &&
         isLegalInteger(I.getOperand(0)->getType()->getScalarSizeInBits()))
     {
-        //Need to see if it is safe to replace, combine, or wipe out
+        //Need to see if it is safe to wipe it out. It is safe only if the user is a
+        //SExt or ZExt and the trunc starting bitwidth is less than the
+        //users bitwidth.
         Value* new_inst = NULL;
         Instruction* castInst = I.user_back();
         auto Src = I.getOperand(0);
         auto Src_bitsize = Src->getType()->getScalarSizeInBits();
-        auto Trunc_bitsize = I.getType()->getScalarSizeInBits();
         auto castInst_bitsize = castInst->getType()->getScalarSizeInBits();
-        if (Src_bitsize <= castInst_bitsize)
+        if (Src_bitsize < castInst_bitsize)
         {
-            //Example 1:
-            //%a = trunc i8 %in to i5
-            //%out = sext i5 %a to i32
-            //=>
-            //%q = zext i8 %in to i32
-            //%s = shl i32 %q, 27
-            //%out = ashr i32 %s, 27
-
-            //Example 2:
-            //%a = trunc i8 %in to i5
-            //%out = zext i5 %a to i32
-            //=>
-            //%q = and i8 %in, 31
-            //%out = zext i8 %q to i32
-
             if (isa<SExtInst>(castInst))
-            {
-                auto shiftAmt = castInst_bitsize - Trunc_bitsize;
-                auto inst1 = m_builder->CreateZExt(Src, castInst->getType());
-                auto inst2 = m_builder->CreateShl(inst1, shiftAmt);
-                new_inst = m_builder->CreateAShr(inst2, shiftAmt);
-            }
-            else if (isa<ZExtInst>(castInst))
-            {
-                auto inst1 = m_builder->CreateAnd(Src, (1 << Trunc_bitsize) - 1);
-                new_inst = m_builder->CreateZExt(inst1, castInst->getType());
-            }
-        }
-        else if (Src_bitsize > castInst_bitsize)
-        {
-            //Most likely a trunc instruction lets combine these two truncs and try again
-            //Example:
-            //%261 = trunc i8 %260 to i5
-            //%262 = trunc i5 %261 to i3
-            //------>
-            //%out = trunc i8 %260 to i3
-            if (isa<TruncInst>(castInst))
-            {
-                auto new_val = m_builder->CreateTrunc(Src, castInst->getType());
-                castInst->replaceAllUsesWith(new_val);
-                if (auto *new_trunc = dyn_cast<TruncInst>(new_val))
-                    cleanupTruncInst(*new_trunc);
-                Changed = true;
-            }
+                new_inst = m_builder->CreateSExt(Src, castInst->getType());
+            if (isa<ZExtInst>(castInst))
+                new_inst = m_builder->CreateZExt(Src, castInst->getType());
         }
 
         if (new_inst != NULL)