diff --git a/flang/include/flang/Lower/IntrinsicCall.h b/flang/include/flang/Optimizer/Builder/IntrinsicCall.h
rename from flang/include/flang/Lower/IntrinsicCall.h
rename to flang/include/flang/Optimizer/Builder/IntrinsicCall.h
--- a/flang/include/flang/Lower/IntrinsicCall.h
+++ b/flang/include/flang/Optimizer/Builder/IntrinsicCall.h
@@ -1,4 +1,4 @@
-//===-- Lower/IntrinsicCall.h -- lowering of intrinsics ---------*- C++ -*-===//
+//===-- Builder/IntrinsicCall.h -- lowering of intrinsics -------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -12,7 +12,7 @@
 #include "flang/Optimizer/Builder/FIRBuilder.h"
 #include <optional>
 
-namespace Fortran::lower {
+namespace fir {
 
 class StatementContext;
 
@@ -103,6 +103,6 @@
 mlir::Value genPow(fir::FirOpBuilder &, mlir::Location, mlir::Type resultType,
                    mlir::Value x, mlir::Value y);
 
-} // namespace Fortran::lower
+} // namespace fir
 
 #endif // FORTRAN_LOWER_INTRINSICCALL_H
diff --git a/flang/lib/Lower/CMakeLists.txt b/flang/lib/Lower/CMakeLists.txt
--- a/flang/lib/Lower/CMakeLists.txt
+++ b/flang/lib/Lower/CMakeLists.txt
@@ -15,7 +15,6 @@
   CustomIntrinsicCall.cpp
   DumpEvaluateExpr.cpp
   HostAssociations.cpp
-  IntrinsicCall.cpp
   IO.cpp
   IterationSpace.cpp
   LoweringOptions.cpp
diff --git a/flang/lib/Lower/ConvertCall.cpp b/flang/lib/Lower/ConvertCall.cpp
--- a/flang/lib/Lower/ConvertCall.cpp
+++ b/flang/lib/Lower/ConvertCall.cpp
@@ -14,12 +14,12 @@
 #include "flang/Lower/ConvertExprToHLFIR.h"
 #include "flang/Lower/ConvertVariable.h"
 #include "flang/Lower/CustomIntrinsicCall.h"
-#include "flang/Lower/IntrinsicCall.h"
 #include "flang/Lower/StatementContext.h"
 #include "flang/Lower/SymbolMap.h"
 #include "flang/Optimizer/Builder/BoxValue.h"
 #include "flang/Optimizer/Builder/Character.h"
 #include "flang/Optimizer/Builder/FIRBuilder.h"
+#include "flang/Optimizer/Builder/IntrinsicCall.h"
 #include "flang/Optimizer/Builder/LowLevelIntrinsics.h"
 #include "flang/Optimizer/Builder/MutableBox.h"
 #include "flang/Optimizer/Builder/Runtime/Derived.h"
@@ -1074,11 +1074,11 @@
 
 /// Lower calls to intrinsic procedures with actual arguments that have been
 /// pre-lowered but have not yet been prepared according to the interface.
-static std::optional<hlfir::EntityWithAttributes> genIntrinsicRefCore(
-    PreparedActualArguments &loweredActuals,
-    const Fortran::evaluate::SpecificIntrinsic &intrinsic,
-    const Fortran::lower::IntrinsicArgumentLoweringRules *argLowering,
-    CallContext &callContext) {
+static std::optional<hlfir::EntityWithAttributes>
+genIntrinsicRefCore(PreparedActualArguments &loweredActuals,
+                    const Fortran::evaluate::SpecificIntrinsic &intrinsic,
+                    const fir::IntrinsicArgumentLoweringRules *argLowering,
+                    CallContext &callContext) {
   llvm::SmallVector<fir::ExtendedValue> operands;
   auto &stmtCtx = callContext.stmtCtx;
   auto &converter = callContext.converter;
@@ -1086,7 +1086,7 @@
   mlir::Location loc = callContext.loc;
   for (auto arg : llvm::enumerate(loweredActuals)) {
     if (!arg.value()) {
-      operands.emplace_back(Fortran::lower::getAbsentIntrinsicArgument());
+      operands.emplace_back(fir::getAbsentIntrinsicArgument());
       continue;
     }
     if (arg.value()->handleDynamicOptional())
@@ -1099,22 +1099,22 @@
       continue;
     }
     // Ad-hoc argument lowering handling.
-    Fortran::lower::ArgLoweringRule argRules =
-        Fortran::lower::lowerIntrinsicArgumentAs(*argLowering, arg.index());
+    fir::ArgLoweringRule argRules =
+        fir::lowerIntrinsicArgumentAs(*argLowering, arg.index());
     switch (argRules.lowerAs) {
-    case Fortran::lower::LowerIntrinsicArgAs::Value:
+    case fir::LowerIntrinsicArgAs::Value:
       operands.emplace_back(
           Fortran::lower::convertToValue(loc, converter, actual, stmtCtx));
       continue;
-    case Fortran::lower::LowerIntrinsicArgAs::Addr:
+    case fir::LowerIntrinsicArgAs::Addr:
       operands.emplace_back(
           Fortran::lower::convertToAddress(loc, converter, actual, stmtCtx));
       continue;
-    case Fortran::lower::LowerIntrinsicArgAs::Box:
+    case fir::LowerIntrinsicArgAs::Box:
       operands.emplace_back(
           Fortran::lower::convertToBox(loc, converter, actual, stmtCtx));
       continue;
-    case Fortran::lower::LowerIntrinsicArgAs::Inquired:
+    case fir::LowerIntrinsicArgAs::Inquired:
       // Place hlfir.expr in memory, and unbox fir.boxchar. Other entities
       // are translated to fir::ExtendedValue without transformation (notably,
       // pointers/allocatable are not dereferenced).
@@ -1134,9 +1134,9 @@
   if (callContext.resultType)
     scalarResultType = hlfir::getFortranElementType(*callContext.resultType);
   // Let the intrinsic library lower the intrinsic procedure call.
-  auto [resultExv, mustBeFreed] = Fortran::lower::genIntrinsicCall(
-      callContext.getBuilder(), loc, intrinsic.name, scalarResultType,
-      operands);
+  auto [resultExv, mustBeFreed] =
+      genIntrinsicCall(callContext.getBuilder(), loc, intrinsic.name,
+                       scalarResultType, operands);
   if (!fir::getBase(resultExv))
     return std::nullopt;
   hlfir::EntityWithAttributes resultEntity = extendedValueToHlfirEntity(
@@ -1326,8 +1326,7 @@
 public:
   ElementalIntrinsicCallBuilder(
       const Fortran::evaluate::SpecificIntrinsic &intrinsic,
-      const Fortran::lower::IntrinsicArgumentLoweringRules *argLowering,
-      bool isFunction)
+      const fir::IntrinsicArgumentLoweringRules *argLowering, bool isFunction)
       : intrinsic{intrinsic}, argLowering{argLowering}, isFunction{isFunction} {
   }
   std::optional<hlfir::Entity>
@@ -1360,7 +1359,7 @@
 
 private:
   const Fortran::evaluate::SpecificIntrinsic &intrinsic;
-  const Fortran::lower::IntrinsicArgumentLoweringRules *argLowering;
+  const fir::IntrinsicArgumentLoweringRules *argLowering;
   const bool isFunction;
 };
 } // namespace
@@ -1408,8 +1407,8 @@
     TODO(loc, "special cases of intrinsic with optional arguments");
 
   PreparedActualArguments loweredActuals;
-  const Fortran::lower::IntrinsicArgumentLoweringRules *argLowering =
-      Fortran::lower::getIntrinsicArgumentLowering(intrinsic.name);
+  const fir::IntrinsicArgumentLoweringRules *argLowering =
+      fir::getIntrinsicArgumentLowering(intrinsic.name);
   for (const auto &arg : llvm::enumerate(callContext.procRef.arguments())) {
     auto *expr =
         Fortran::evaluate::UnwrapExpr<Fortran::lower::SomeExpr>(arg.value());
@@ -1423,8 +1422,8 @@
         callContext.stmtCtx);
     std::optional<mlir::Value> isPresent;
     if (argLowering) {
-      Fortran::lower::ArgLoweringRule argRules =
-          Fortran::lower::lowerIntrinsicArgumentAs(*argLowering, arg.index());
+      fir::ArgLoweringRule argRules =
+          fir::lowerIntrinsicArgumentAs(*argLowering, arg.index());
       if (argRules.handleDynamicOptional)
         isPresent =
             genIsPresentIfArgMaybeAbsent(loc, loweredActual, *expr, callContext,
diff --git a/flang/lib/Lower/ConvertExpr.cpp b/flang/lib/Lower/ConvertExpr.cpp
--- a/flang/lib/Lower/ConvertExpr.cpp
+++ b/flang/lib/Lower/ConvertExpr.cpp
@@ -28,13 +28,13 @@
 #include "flang/Lower/ConvertVariable.h"
 #include "flang/Lower/CustomIntrinsicCall.h"
 #include "flang/Lower/DumpEvaluateExpr.h"
-#include "flang/Lower/IntrinsicCall.h"
 #include "flang/Lower/Mangler.h"
 #include "flang/Lower/Runtime.h"
 #include "flang/Lower/Support/Utils.h"
 #include "flang/Optimizer/Builder/Character.h"
 #include "flang/Optimizer/Builder/Complex.h"
 #include "flang/Optimizer/Builder/Factory.h"
+#include "flang/Optimizer/Builder/IntrinsicCall.h"
 #include "flang/Optimizer/Builder/Runtime/Assign.h"
 #include "flang/Optimizer/Builder/Runtime/Character.h"
 #include "flang/Optimizer/Builder/Runtime/Derived.h"
@@ -897,8 +897,8 @@
           converter.getFoldingContext().intrinsics().GetGenericIntrinsicName(
               intrinsic->name);
       mlir::SymbolRefAttr symbolRefAttr =
-          Fortran::lower::getUnrestrictedIntrinsicSymbolRefAttr(
-              builder, loc, genericName, signature);
+          fir::getUnrestrictedIntrinsicSymbolRefAttr(builder, loc, genericName,
+                                                     signature);
       mlir::Value funcPtr =
           builder.create<fir::AddrOfOp>(loc, signature, symbolRefAttr);
       return funcPtr;
@@ -1150,7 +1150,7 @@
     mlir::Type ty = converter.genType(TC, KIND);
     mlir::Value lhs = genunbox(op.left());
     mlir::Value rhs = genunbox(op.right());
-    return Fortran::lower::genPow(builder, getLoc(), ty, lhs, rhs);
+    return fir::genPow(builder, getLoc(), ty, lhs, rhs);
   }
 
   template <Fortran::common::TypeCategory TC, int KIND>
@@ -1160,7 +1160,7 @@
     mlir::Type ty = converter.genType(TC, KIND);
     mlir::Value lhs = genunbox(op.left());
     mlir::Value rhs = genunbox(op.right());
-    return Fortran::lower::genPow(builder, getLoc(), ty, lhs, rhs);
+    return fir::genPow(builder, getLoc(), ty, lhs, rhs);
   }
 
   template <int KIND>
@@ -1191,11 +1191,11 @@
     mlir::Value rhs = genunbox(op.right());
     switch (op.ordering) {
     case Fortran::evaluate::Ordering::Greater:
-      return Fortran::lower::genMax(builder, getLoc(),
-                                    llvm::ArrayRef<mlir::Value>{lhs, rhs});
+      return fir::genMax(builder, getLoc(),
+                         llvm::ArrayRef<mlir::Value>{lhs, rhs});
     case Fortran::evaluate::Ordering::Less:
-      return Fortran::lower::genMin(builder, getLoc(),
-                                    llvm::ArrayRef<mlir::Value>{lhs, rhs});
+      return fir::genMin(builder, getLoc(),
+                         llvm::ArrayRef<mlir::Value>{lhs, rhs});
     case Fortran::evaluate::Ordering::Equal:
       llvm_unreachable("Equal is not a valid ordering in this context");
     }
@@ -1879,14 +1879,14 @@
           operands.size(), stmtCtx);
     }
 
-    const Fortran::lower::IntrinsicArgumentLoweringRules *argLowering =
-        Fortran::lower::getIntrinsicArgumentLowering(name);
+    const fir::IntrinsicArgumentLoweringRules *argLowering =
+        fir::getIntrinsicArgumentLowering(name);
     for (const auto &arg : llvm::enumerate(procRef.arguments())) {
       auto *expr =
           Fortran::evaluate::UnwrapExpr<Fortran::lower::SomeExpr>(arg.value());
       if (!expr) {
         // Absent optional.
-        operands.emplace_back(Fortran::lower::getAbsentIntrinsicArgument());
+        operands.emplace_back(fir::getAbsentIntrinsicArgument());
         continue;
       }
       if (!argLowering) {
@@ -1895,43 +1895,43 @@
         continue;
       }
       // Ad-hoc argument lowering handling.
-      Fortran::lower::ArgLoweringRule argRules =
-          Fortran::lower::lowerIntrinsicArgumentAs(*argLowering, arg.index());
+      fir::ArgLoweringRule argRules =
+          fir::lowerIntrinsicArgumentAs(*argLowering, arg.index());
       if (argRules.handleDynamicOptional &&
           Fortran::evaluate::MayBePassedAsAbsentOptional(
               *expr, converter.getFoldingContext())) {
         ExtValue optional = lowerIntrinsicArgumentAsInquired(*expr);
         mlir::Value isPresent = genActualIsPresentTest(builder, loc, optional);
         switch (argRules.lowerAs) {
-        case Fortran::lower::LowerIntrinsicArgAs::Value:
+        case fir::LowerIntrinsicArgAs::Value:
           operands.emplace_back(
               genOptionalValue(builder, loc, optional, isPresent));
           continue;
-        case Fortran::lower::LowerIntrinsicArgAs::Addr:
+        case fir::LowerIntrinsicArgAs::Addr:
           operands.emplace_back(
               genOptionalAddr(builder, loc, optional, isPresent));
           continue;
-        case Fortran::lower::LowerIntrinsicArgAs::Box:
+        case fir::LowerIntrinsicArgAs::Box:
           operands.emplace_back(
               genOptionalBox(builder, loc, optional, isPresent));
           continue;
-        case Fortran::lower::LowerIntrinsicArgAs::Inquired:
+        case fir::LowerIntrinsicArgAs::Inquired:
           operands.emplace_back(optional);
           continue;
         }
         llvm_unreachable("bad switch");
       }
       switch (argRules.lowerAs) {
-      case Fortran::lower::LowerIntrinsicArgAs::Value:
+      case fir::LowerIntrinsicArgAs::Value:
         operands.emplace_back(genval(*expr));
         continue;
-      case Fortran::lower::LowerIntrinsicArgAs::Addr:
+      case fir::LowerIntrinsicArgAs::Addr:
         operands.emplace_back(gen(*expr));
         continue;
-      case Fortran::lower::LowerIntrinsicArgAs::Box:
+      case fir::LowerIntrinsicArgAs::Box:
         operands.emplace_back(lowerIntrinsicArgumentAsBox(*expr));
         continue;
-      case Fortran::lower::LowerIntrinsicArgAs::Inquired:
+      case fir::LowerIntrinsicArgAs::Inquired:
         operands.emplace_back(lowerIntrinsicArgumentAsInquired(*expr));
         continue;
       }
@@ -4477,8 +4477,8 @@
     std::string name =
         intrinsic ? intrinsic->name
                   : procRef.proc().GetSymbol()->GetUltimate().name().ToString();
-    const Fortran::lower::IntrinsicArgumentLoweringRules *argLowering =
-        Fortran::lower::getIntrinsicArgumentLowering(name);
+    const fir::IntrinsicArgumentLoweringRules *argLowering =
+        fir::getIntrinsicArgumentLowering(name);
     mlir::Location loc = getLoc();
     if (intrinsic && Fortran::lower::intrinsicRequiresCustomOptionalHandling(
                          procRef, *intrinsic, converter)) {
@@ -4533,15 +4533,15 @@
         operands.emplace_back(genElementalArgument(*expr));
       } else {
         // Ad-hoc argument lowering handling.
-        Fortran::lower::ArgLoweringRule argRules =
-            Fortran::lower::lowerIntrinsicArgumentAs(*argLowering, arg.index());
+        fir::ArgLoweringRule argRules =
+            fir::lowerIntrinsicArgumentAs(*argLowering, arg.index());
         if (argRules.handleDynamicOptional &&
             Fortran::evaluate::MayBePassedAsAbsentOptional(
                 *expr, converter.getFoldingContext())) {
           // Currently, there is not elemental intrinsic that requires lowering
           // a potentially absent argument to something else than a value (apart
           // from character MAX/MIN that are handled elsewhere.)
-          if (argRules.lowerAs != Fortran::lower::LowerIntrinsicArgAs::Value)
+          if (argRules.lowerAs != fir::LowerIntrinsicArgAs::Value)
             TODO(loc, "non trivial optional elemental intrinsic array "
                       "argument");
           PushSemantics(ConstituentSemantics::RefTransparent);
@@ -4549,23 +4549,23 @@
           continue;
         }
         switch (argRules.lowerAs) {
-        case Fortran::lower::LowerIntrinsicArgAs::Value: {
+        case fir::LowerIntrinsicArgAs::Value: {
           PushSemantics(ConstituentSemantics::RefTransparent);
           operands.emplace_back(genElementalArgument(*expr));
         } break;
-        case Fortran::lower::LowerIntrinsicArgAs::Addr: {
+        case fir::LowerIntrinsicArgAs::Addr: {
           // Note: assume does not have Fortran VALUE attribute semantics.
           PushSemantics(ConstituentSemantics::RefOpaque);
           operands.emplace_back(genElementalArgument(*expr));
         } break;
-        case Fortran::lower::LowerIntrinsicArgAs::Box: {
+        case fir::LowerIntrinsicArgAs::Box: {
           PushSemantics(ConstituentSemantics::RefOpaque);
           auto lambda = genElementalArgument(*expr);
           operands.emplace_back([=](IterSpace iters) {
             return builder.createBox(loc, lambda(iters));
           });
         } break;
-        case Fortran::lower::LowerIntrinsicArgAs::Inquired:
+        case fir::LowerIntrinsicArgAs::Inquired:
           TODO(loc, "intrinsic function with inquired argument");
           break;
         }
@@ -5045,7 +5045,7 @@
     return [=](IterSpace iters) -> ExtValue {
       mlir::Value lhs = fir::getBase(lf(iters));
       mlir::Value rhs = fir::getBase(rf(iters));
-      return Fortran::lower::genPow(builder, loc, ty, lhs, rhs);
+      return fir::genPow(builder, loc, ty, lhs, rhs);
     };
   }
   template <Fortran::common::TypeCategory TC, int KIND>
@@ -5059,15 +5059,13 @@
       return [=](IterSpace iters) -> ExtValue {
         mlir::Value lhs = fir::getBase(lf(iters));
         mlir::Value rhs = fir::getBase(rf(iters));
-        return Fortran::lower::genMax(builder, loc,
-                                      llvm::ArrayRef<mlir::Value>{lhs, rhs});
+        return fir::genMax(builder, loc, llvm::ArrayRef<mlir::Value>{lhs, rhs});
       };
     case Fortran::evaluate::Ordering::Less:
       return [=](IterSpace iters) -> ExtValue {
         mlir::Value lhs = fir::getBase(lf(iters));
         mlir::Value rhs = fir::getBase(rf(iters));
-        return Fortran::lower::genMin(builder, loc,
-                                      llvm::ArrayRef<mlir::Value>{lhs, rhs});
+        return fir::genMin(builder, loc, llvm::ArrayRef<mlir::Value>{lhs, rhs});
       };
     case Fortran::evaluate::Ordering::Equal:
       llvm_unreachable("Equal is not a valid ordering in this context");
@@ -5085,7 +5083,7 @@
     return [=](IterSpace iters) {
       mlir::Value lhs = fir::getBase(lf(iters));
       mlir::Value rhs = fir::getBase(rf(iters));
-      return Fortran::lower::genPow(builder, loc, ty, lhs, rhs);
+      return fir::genPow(builder, loc, ty, lhs, rhs);
     };
   }
   template <int KIND>
diff --git a/flang/lib/Lower/ConvertExprToHLFIR.cpp b/flang/lib/Lower/ConvertExprToHLFIR.cpp
--- a/flang/lib/Lower/ConvertExprToHLFIR.cpp
+++ b/flang/lib/Lower/ConvertExprToHLFIR.cpp
@@ -18,10 +18,10 @@
 #include "flang/Lower/ConvertConstant.h"
 #include "flang/Lower/ConvertType.h"
 #include "flang/Lower/ConvertVariable.h"
-#include "flang/Lower/IntrinsicCall.h"
 #include "flang/Lower/StatementContext.h"
 #include "flang/Lower/SymbolMap.h"
 #include "flang/Optimizer/Builder/Complex.h"
+#include "flang/Optimizer/Builder/IntrinsicCall.h"
 #include "flang/Optimizer/Builder/MutableBox.h"
 #include "flang/Optimizer/Builder/Runtime/Character.h"
 #include "flang/Optimizer/Builder/Todo.h"
@@ -614,8 +614,7 @@
                                          hlfir::Entity lhs, hlfir::Entity rhs) {
     mlir::Type ty = Fortran::lower::getFIRType(builder.getContext(), TC, KIND,
                                                /*params=*/std::nullopt);
-    return hlfir::EntityWithAttributes{
-        Fortran::lower::genPow(builder, loc, ty, lhs, rhs)};
+    return hlfir::EntityWithAttributes{fir::genPow(builder, loc, ty, lhs, rhs)};
   }
 };
 
@@ -629,8 +628,7 @@
                                          hlfir::Entity lhs, hlfir::Entity rhs) {
     mlir::Type ty = Fortran::lower::getFIRType(builder.getContext(), TC, KIND,
                                                /*params=*/std::nullopt);
-    return hlfir::EntityWithAttributes{
-        Fortran::lower::genPow(builder, loc, ty, lhs, rhs)};
+    return hlfir::EntityWithAttributes{fir::genPow(builder, loc, ty, lhs, rhs)};
   }
 };
 
@@ -644,8 +642,8 @@
                                          hlfir::Entity rhs) {
     llvm::SmallVector<mlir::Value, 2> args{lhs, rhs};
     fir::ExtendedValue res = op.ordering == Fortran::evaluate::Ordering::Greater
-                                 ? Fortran::lower::genMax(builder, loc, args)
-                                 : Fortran::lower::genMin(builder, loc, args);
+                                 ? fir::genMax(builder, loc, args)
+                                 : fir::genMin(builder, loc, args);
     return hlfir::EntityWithAttributes{fir::getBase(res)};
   }
 };
diff --git a/flang/lib/Lower/ConvertVariable.cpp b/flang/lib/Lower/ConvertVariable.cpp
--- a/flang/lib/Lower/ConvertVariable.cpp
+++ b/flang/lib/Lower/ConvertVariable.cpp
@@ -18,7 +18,6 @@
 #include "flang/Lower/ConvertConstant.h"
 #include "flang/Lower/ConvertExpr.h"
 #include "flang/Lower/ConvertExprToHLFIR.h"
-#include "flang/Lower/IntrinsicCall.h"
 #include "flang/Lower/Mangler.h"
 #include "flang/Lower/PFTBuilder.h"
 #include "flang/Lower/StatementContext.h"
@@ -27,6 +26,7 @@
 #include "flang/Optimizer/Builder/Character.h"
 #include "flang/Optimizer/Builder/FIRBuilder.h"
 #include "flang/Optimizer/Builder/HLFIRTools.h"
+#include "flang/Optimizer/Builder/IntrinsicCall.h"
 #include "flang/Optimizer/Builder/Runtime/Derived.h"
 #include "flang/Optimizer/Builder/Todo.h"
 #include "flang/Optimizer/Dialect/FIRAttr.h"
diff --git a/flang/lib/Lower/CustomIntrinsicCall.cpp b/flang/lib/Lower/CustomIntrinsicCall.cpp
--- a/flang/lib/Lower/CustomIntrinsicCall.cpp
+++ b/flang/lib/Lower/CustomIntrinsicCall.cpp
@@ -14,8 +14,8 @@
 #include "flang/Evaluate/expression.h"
 #include "flang/Evaluate/fold.h"
 #include "flang/Evaluate/tools.h"
-#include "flang/Lower/IntrinsicCall.h"
 #include "flang/Lower/StatementContext.h"
+#include "flang/Optimizer/Builder/IntrinsicCall.h"
 #include "flang/Optimizer/Builder/Todo.h"
 #include <optional>
 
@@ -74,7 +74,7 @@
                                  llvm::ArrayRef<fir::ExtendedValue> args,
                                  Fortran::lower::StatementContext &stmtCtx) {
   auto [result, mustBeFreed] =
-      Fortran::lower::genIntrinsicCall(builder, loc, name, resultType, args);
+      fir::genIntrinsicCall(builder, loc, name, resultType, args);
   if (mustBeFreed) {
     mlir::Value addr = fir::getBase(result);
     if (auto *box = result.getBoxOf<fir::BoxValue>())
diff --git a/flang/lib/Optimizer/Builder/CMakeLists.txt b/flang/lib/Optimizer/Builder/CMakeLists.txt
--- a/flang/lib/Optimizer/Builder/CMakeLists.txt
+++ b/flang/lib/Optimizer/Builder/CMakeLists.txt
@@ -7,6 +7,7 @@
   DoLoopHelper.cpp
   FIRBuilder.cpp
   HLFIRTools.cpp
+  IntrinsicCall.cpp
   LowLevelIntrinsics.cpp
   MutableBox.cpp
   Runtime/Allocatable.cpp
diff --git a/flang/lib/Lower/IntrinsicCall.cpp b/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
rename from flang/lib/Lower/IntrinsicCall.cpp
rename to flang/lib/Optimizer/Builder/IntrinsicCall.cpp
--- a/flang/lib/Lower/IntrinsicCall.cpp
+++ b/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
@@ -13,7 +13,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "flang/Lower/IntrinsicCall.h"
+#include "flang/Optimizer/Builder/IntrinsicCall.h"
 #include "flang/Common/static-multimap-view.h"
 #include "flang/Optimizer/Builder/BoxValue.h"
 #include "flang/Optimizer/Builder/Character.h"
@@ -101,7 +101,7 @@
   // possible to implement it without some target dependent runtime.
 };
 
-fir::ExtendedValue Fortran::lower::getAbsentIntrinsicArgument() {
+fir::ExtendedValue fir::getAbsentIntrinsicArgument() {
   return fir::UnboxedValue{};
 }
 
@@ -411,13 +411,12 @@
 
 struct IntrinsicDummyArgument {
   const char *name = nullptr;
-  Fortran::lower::LowerIntrinsicArgAs lowerAs =
-      Fortran::lower::LowerIntrinsicArgAs::Value;
+  fir::LowerIntrinsicArgAs lowerAs = fir::LowerIntrinsicArgAs::Value;
   bool handleDynamicOptional = false;
 };
 
 /// This is shared by intrinsics and intrinsic module procedures.
-struct Fortran::lower::IntrinsicArgumentLoweringRules {
+struct fir::IntrinsicArgumentLoweringRules {
   /// There is no more than 7 non repeated arguments in Fortran intrinsics.
   IntrinsicDummyArgument args[7];
   constexpr bool hasDefaultRules() const { return args[0].name == nullptr; }
@@ -429,17 +428,17 @@
   const char *name;
   IntrinsicLibrary::Generator generator;
   // The following may be omitted in the table below.
-  Fortran::lower::IntrinsicArgumentLoweringRules argLoweringRules = {};
+  fir::IntrinsicArgumentLoweringRules argLoweringRules = {};
   bool isElemental = true;
   /// Code heavy intrinsic can be outlined to make FIR
   /// more readable.
   bool outline = false;
 };
 
-constexpr auto asValue = Fortran::lower::LowerIntrinsicArgAs::Value;
-constexpr auto asAddr = Fortran::lower::LowerIntrinsicArgAs::Addr;
-constexpr auto asBox = Fortran::lower::LowerIntrinsicArgAs::Box;
-constexpr auto asInquired = Fortran::lower::LowerIntrinsicArgAs::Inquired;
+constexpr auto asValue = fir::LowerIntrinsicArgAs::Value;
+constexpr auto asAddr = fir::LowerIntrinsicArgAs::Addr;
+constexpr auto asBox = fir::LowerIntrinsicArgAs::Box;
+constexpr auto asInquired = fir::LowerIntrinsicArgAs::Inquired;
 using I = IntrinsicLibrary;
 
 /// Flag to indicate that an intrinsic argument has to be handled as
@@ -5335,8 +5334,8 @@
 // procedure.
 //===----------------------------------------------------------------------===//
 
-const Fortran::lower::IntrinsicArgumentLoweringRules *
-Fortran::lower::getIntrinsicArgumentLowering(llvm::StringRef specificName) {
+const fir::IntrinsicArgumentLoweringRules *
+fir::getIntrinsicArgumentLowering(llvm::StringRef specificName) {
   llvm::StringRef name = genericName(specificName);
   if (const IntrinsicHandler *handler = findIntrinsicHandler(name))
     if (!handler->argLoweringRules.hasDefaultRules())
@@ -5346,8 +5345,9 @@
 
 /// Return how argument \p argName should be lowered given the rules for the
 /// intrinsic function.
-Fortran::lower::ArgLoweringRule Fortran::lower::lowerIntrinsicArgumentAs(
-    const IntrinsicArgumentLoweringRules &rules, unsigned position) {
+fir::ArgLoweringRule
+fir::lowerIntrinsicArgumentAs(const IntrinsicArgumentLoweringRules &rules,
+                              unsigned position) {
   assert(position < sizeof(rules.args) / (sizeof(decltype(*rules.args))) &&
          "invalid argument");
   return {rules.args[position].lowerAs,
@@ -5359,35 +5359,32 @@
 //===----------------------------------------------------------------------===//
 
 std::pair<fir::ExtendedValue, bool>
-Fortran::lower::genIntrinsicCall(fir::FirOpBuilder &builder, mlir::Location loc,
-                                 llvm::StringRef name,
-                                 std::optional<mlir::Type> resultType,
-                                 llvm::ArrayRef<fir::ExtendedValue> args) {
+fir::genIntrinsicCall(fir::FirOpBuilder &builder, mlir::Location loc,
+                      llvm::StringRef name,
+                      std::optional<mlir::Type> resultType,
+                      llvm::ArrayRef<fir::ExtendedValue> args) {
   return IntrinsicLibrary{builder, loc}.genIntrinsicCall(name, resultType,
                                                          args);
 }
 
-mlir::Value Fortran::lower::genMax(fir::FirOpBuilder &builder,
-                                   mlir::Location loc,
-                                   llvm::ArrayRef<mlir::Value> args) {
+mlir::Value fir::genMax(fir::FirOpBuilder &builder, mlir::Location loc,
+                        llvm::ArrayRef<mlir::Value> args) {
   assert(args.size() > 0 && "max requires at least one argument");
   return IntrinsicLibrary{builder, loc}
       .genExtremum<Extremum::Max, ExtremumBehavior::MinMaxss>(args[0].getType(),
                                                               args);
 }
 
-mlir::Value Fortran::lower::genMin(fir::FirOpBuilder &builder,
-                                   mlir::Location loc,
-                                   llvm::ArrayRef<mlir::Value> args) {
+mlir::Value fir::genMin(fir::FirOpBuilder &builder, mlir::Location loc,
+                        llvm::ArrayRef<mlir::Value> args) {
   assert(args.size() > 0 && "min requires at least one argument");
   return IntrinsicLibrary{builder, loc}
       .genExtremum<Extremum::Min, ExtremumBehavior::MinMaxss>(args[0].getType(),
                                                               args);
 }
 
-mlir::Value Fortran::lower::genPow(fir::FirOpBuilder &builder,
-                                   mlir::Location loc, mlir::Type type,
-                                   mlir::Value x, mlir::Value y) {
+mlir::Value fir::genPow(fir::FirOpBuilder &builder, mlir::Location loc,
+                        mlir::Type type, mlir::Value x, mlir::Value y) {
   // TODO: since there is no libm version of pow with integer exponent,
   //       we have to provide an alternative implementation for
   //       "precise/strict" FP mode.
@@ -5398,7 +5395,7 @@
   return IntrinsicLibrary{builder, loc}.genRuntimeCall("pow", type, {x, y});
 }
 
-mlir::SymbolRefAttr Fortran::lower::getUnrestrictedIntrinsicSymbolRefAttr(
+mlir::SymbolRefAttr fir::getUnrestrictedIntrinsicSymbolRefAttr(
     fir::FirOpBuilder &builder, mlir::Location loc, llvm::StringRef name,
     mlir::FunctionType signature) {
   return IntrinsicLibrary{builder, loc}.getUnrestrictedIntrinsicSymbolRefAttr(