Introduction of new entry in IGC constant folder for bfi.

Author: krystian-andrzejewski

IGC/Compiler/CustomSafeOptPass.cpp

@@ -440,8 +440,10 @@ void CustomSafeOptPass::visitCallInst(CallInst& C)
         }
 
         case GenISAIntrinsic::GenISA_bfi:
+        {
             visitBfi(inst);
             break;
+        }
 
         case GenISAIntrinsic::GenISA_f32tof16_rtz:
         {
@@ -3077,6 +3079,21 @@ Constant* IGCConstProp::ConstantFoldCallInstruction(CallInst* inst)
             }
         }
         break;
+        case llvm_bfi:
+        {
+            Constant* C1 = dyn_cast<Constant>(inst->getOperand(1));
+            Constant* C2 = dyn_cast<Constant>(inst->getOperand(2));
+            Constant* C3 = dyn_cast<Constant>(inst->getOperand(3));
+            if (C0 && C0->isZeroValue() && C3)
+            {
+                C = C3;
+            }
+            else if (C0 && C1 && C2 && C3)
+            {
+                C = constantFolder.CreateBfi(C0, C1, C2, C3);
+            }
+        }
+        break;
         default:
             break;
         }

IGC/common/IGCConstantFolder.cpp

@@ -315,4 +315,24 @@ llvm::Constant* IGCConstantFolder::CreateFirstBitLo(llvm::Constant* C0) const
     return llvm::ConstantInt::get(C0->getType(), fbl);
 }
 
+llvm::Constant* IGCConstantFolder::CreateBfi(llvm::Constant* C0, llvm::Constant* C1, llvm::Constant* C2, llvm::Constant* C3) const
+{
+    if (llvm::isa<llvm::UndefValue>(C0) || llvm::isa<llvm::UndefValue>(C1) || llvm::isa<llvm::UndefValue>(C2))
+    {
+        return nullptr;
+    }
+    llvm::ConstantInt* CI0 = llvm::cast<llvm::ConstantInt>(C0); // width
+    llvm::ConstantInt* CI1 = llvm::cast<llvm::ConstantInt>(C1); // offset
+    llvm::ConstantInt* CI2 = llvm::cast<llvm::ConstantInt>(C2); // the number the bits are taken from.
+    llvm::ConstantInt* CI3 = llvm::cast<llvm::ConstantInt>(C3); // the number with bits to be replaced.
+    uint32_t width = int_cast<uint32_t>(CI0->getZExtValue());
+    uint32_t offset = int_cast<uint32_t>(CI1->getZExtValue());
+    uint32_t bitwidth = CI2->getType()->getBitWidth();
+    llvm::APInt bitmask = llvm::APInt::getBitsSet(bitwidth, offset, offset + width);
+    llvm::APInt result = CI2->getValue();
+    result = result.shl(offset);
+    result = (result & bitmask) | (CI3->getValue() & ~bitmask);
+    return llvm::ConstantInt::get(C0->getContext(), result);
+}
+
 } // namespace IGC

IGC/common/IGCConstantFolder.h

@@ -59,6 +59,7 @@ class IGCConstantFolder
     llvm::Constant* CreateFirstBitHi(llvm::Constant* C0) const;
     llvm::Constant* CreateFirstBitShi(llvm::Constant* C0) const;
     llvm::Constant* CreateFirstBitLo(llvm::Constant* C0) const;
+    llvm::Constant* CreateBfi(llvm::Constant* C0, llvm::Constant* C1, llvm::Constant* C2, llvm::Constant* C3) const;
 
 
     //===-------------