diff --git a/flang/include/flang/Optimizer/HLFIR/HLFIROps.td b/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
--- a/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
+++ b/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
@@ -319,13 +319,15 @@
   let hasVerifier = 1;
 }
 
-def hlfir_ConcatOp : hlfir_Op<"concat", []> {
+// Allocation effect is because this creates a hlfir.expr, which must be
+// destroyed (only once)
+def hlfir_ConcatOp : hlfir_Op<"concat", [MemoryEffects<[MemAlloc]>]> {
   let summary = "concatenate characters";
   let description = [{
     Concatenate two or more character strings of a same character kind.
   }];
 
-  let arguments = (ins Variadic<AnyScalarCharacterEntity>:$strings,
+  let arguments = (ins Arg<Variadic<AnyScalarCharacterEntity>, "", [MemRead]>:$strings,
                    AnyIntegerType:$length);
 
   let results = (outs AnyScalarCharacterExpr);
@@ -340,7 +342,9 @@
   let hasVerifier = 1;
 }
 
-def hlfir_AllOp : hlfir_Op<"all", []> {
+// Allocation effect is because this might create a hlfir.expr, which must be
+// destroyed (only once)
+def hlfir_AllOp : hlfir_Op<"all", [MemoryEffects<[MemAlloc]>]> {
   let summary = "ALL transformational intrinsic";
   let description = [{
     Takes a logical array MASK as argument, optionally along a particular dimension,
@@ -348,7 +352,7 @@
   }];
 
   let arguments = (ins
-    AnyFortranLogicalArrayObject:$mask,
+    Arg<AnyFortranLogicalArrayObject, "", [MemRead]>:$mask,
     Optional<AnyIntegerType>:$dim
   );
 
@@ -361,7 +365,9 @@
   let hasVerifier = 1;
 }
 
-def hlfir_AnyOp : hlfir_Op<"any", []> {
+// Allocation effect is because this might create a hlfir.expr, which must be
+// destroyed (only once)
+def hlfir_AnyOp : hlfir_Op<"any", [MemoryEffects<[MemAlloc]>]> {
   let summary = "ANY transformational intrinsic";
   let description = [{
     Takes a logical array MASK as argument, optionally along a particular dimension,
@@ -369,7 +375,7 @@
   }];
 
   let arguments = (ins
-    AnyFortranLogicalArrayObject:$mask,
+    Arg<AnyFortranLogicalArrayObject, "", [MemRead]>:$mask,
     Optional<AnyIntegerType>:$dim
   );
 
@@ -382,14 +388,16 @@
   let hasVerifier = 1;
 }
 
-def hlfir_CountOp : hlfir_Op<"count", [AttrSizedOperandSegments]> {
+// Allocation effect is because this might create a hlfir.expr, which must be
+// destroyed (only once)
+def hlfir_CountOp : hlfir_Op<"count", [AttrSizedOperandSegments, MemoryEffects<[MemAlloc]>]> {
   let summary = "COUNT transformational intrinsic";
   let description = [{
     Takes a logical and counts the number of true values.
   }];
 
   let arguments = (ins
-    AnyFortranLogicalArrayObject:$mask,
+    Arg<AnyFortranLogicalArrayObject, "", [MemRead]>:$mask,
     Optional<AnyIntegerType>:$dim,
     Optional<AnyIntegerType>:$kind
   );
@@ -403,9 +411,11 @@
   let hasVerifier = 1;
 }
 
-
+// Allocation effect is because this might create a hlfir.expr, which must be
+// destroyed (only once)
 def hlfir_ProductOp : hlfir_Op<"product", [AttrSizedOperandSegments,
-    DeclareOpInterfaceMethods<ArithFastMathInterface>]> {
+    DeclareOpInterfaceMethods<ArithFastMathInterface>,
+    MemoryEffects<[MemAlloc]>]> {
   let summary = "PRODUCT transformational intrinsic";
   let description = [{
     Multiplies the elements of an array, optionally along a particular dimension,
@@ -413,9 +423,9 @@
   }];
 
   let arguments = (ins
-    AnyFortranNumericalArrayObject:$array,
+    Arg<AnyFortranNumericalArrayObject, "", [MemRead]>:$array,
     Optional<AnyIntegerType>:$dim,
-    Optional<AnyFortranLogicalOrI1ArrayObject>:$mask,
+    Arg<Optional<AnyFortranLogicalOrI1ArrayObject>, "", [MemRead]>:$mask,
     DefaultValuedAttr<Arith_FastMathAttr,
                       "::mlir::arith::FastMathFlags::none">:$fastmath
   );
@@ -429,14 +439,16 @@
   let hasVerifier = 1;
 }
 
-def hlfir_SetLengthOp : hlfir_Op<"set_length", []> {
+// Allocation effect is because this might create a hlfir.expr, which must be
+// destroyed (only once)
+def hlfir_SetLengthOp : hlfir_Op<"set_length", [MemoryEffects<[MemAlloc]>]> {
   let summary = "change the length of a character entity";
   let description = [{
     Change the length of character entity. This trims or pads the
     character argument according to the new length.
   }];
 
-  let arguments = (ins AnyScalarCharacterEntity:$string,
+  let arguments = (ins Arg<AnyScalarCharacterEntity, "", [MemRead]>:$string,
                    AnyIntegerType:$length);
 
   let results = (outs AnyScalarCharacterExpr);
@@ -467,8 +479,11 @@
   let hasCanonicalizeMethod = 1;
 }
 
+// Allocation effect is because this might create a hlfir.expr, which must be
+// destroyed (only once)
 def hlfir_SumOp : hlfir_Op<"sum", [AttrSizedOperandSegments,
-    DeclareOpInterfaceMethods<ArithFastMathInterface>]> {
+    DeclareOpInterfaceMethods<ArithFastMathInterface>,
+    MemoryEffects<[MemAlloc]>]> {
   let summary = "SUM transformational intrinsic";
   let description = [{
     Sums the elements of an array, optionally along a particular dimension,
@@ -476,7 +491,7 @@
   }];
 
   let arguments = (ins
-    AnyFortranNumericalArrayObject:$array,
+    Arg<AnyFortranNumericalArrayObject, "", [MemRead]>:$array,
     Optional<AnyIntegerType>:$dim,
     Optional<AnyFortranLogicalOrI1ArrayObject>:$mask,
     DefaultValuedAttr<Arith_FastMathAttr,
@@ -492,16 +507,19 @@
   let hasVerifier = 1;
 }
 
+// Allocation effect is because this might create a hlfir.expr, which must be
+// destroyed (only once)
 def hlfir_DotProductOp : hlfir_Op<"dot_product",
-    [DeclareOpInterfaceMethods<ArithFastMathInterface>]> {
+    [DeclareOpInterfaceMethods<ArithFastMathInterface>,
+    MemoryEffects<[MemAlloc]>]> {
   let summary = "DOT_PRODUCT transformational intrinsic";
   let description = [{
     Dot product of two vectors
   }];
 
   let arguments = (ins
-    AnyFortranNumericalOrLogicalArrayObject:$lhs,
-    AnyFortranNumericalOrLogicalArrayObject:$rhs,
+    Arg<AnyFortranNumericalOrLogicalArrayObject, "", [MemRead]>:$lhs,
+    Arg<AnyFortranNumericalOrLogicalArrayObject, "", [MemRead]>:$rhs,
     DefaultValuedAttr<Arith_FastMathAttr,
                       "::mlir::arith::FastMathFlags::none">:$fastmath
   );
@@ -515,16 +533,18 @@
   let hasVerifier = 1;
 }
 
+// Allocation effect is because this creates a hlfir.expr, which must be
+// destroyed (only once)
 def hlfir_MatmulOp : hlfir_Op<"matmul",
-    [DeclareOpInterfaceMethods<ArithFastMathInterface>]> {
+    [DeclareOpInterfaceMethods<ArithFastMathInterface>, MemoryEffects<[MemAlloc]>]> {
   let summary = "MATMUL transformational intrinsic";
   let description = [{
     Matrix multiplication
   }];
 
   let arguments = (ins
-    AnyFortranNumericalOrLogicalArrayObject:$lhs,
-    AnyFortranNumericalOrLogicalArrayObject:$rhs,
+    Arg<AnyFortranNumericalOrLogicalArrayObject, "", [MemRead]>:$lhs,
+    Arg<AnyFortranNumericalOrLogicalArrayObject, "", [MemRead]>:$rhs,
     DefaultValuedAttr<Arith_FastMathAttr,
                       "::mlir::arith::FastMathFlags::none">:$fastmath
   );
@@ -541,13 +561,15 @@
   let hasVerifier = 1;
 }
 
-def hlfir_TransposeOp : hlfir_Op<"transpose", []> {
+// Allocation effect is because this creates a hlfir.expr, which must be
+// destroyed (only once)
+def hlfir_TransposeOp : hlfir_Op<"transpose", [MemoryEffects<[MemAlloc]>]> {
   let summary = "TRANSPOSE transformational intrinsic";
   let description = [{
     Transpose a rank 2 array
   }];
 
-  let arguments = (ins AnyFortranArrayObject:$array);
+  let arguments = (ins Arg<AnyFortranArrayObject, "", [MemRead]>:$array);
 
   let results = (outs hlfir_ExprType);
 
@@ -558,16 +580,19 @@
   let hasVerifier = 1;
 }
 
+// Allocation effect is because this creates a hlfir.expr, which must be
+// destroyed (only once)
 def hlfir_MatmulTransposeOp : hlfir_Op<"matmul_transpose",
-    [DeclareOpInterfaceMethods<ArithFastMathInterface>]> {
+    [DeclareOpInterfaceMethods<ArithFastMathInterface>,
+    MemoryEffects<[MemAlloc]>]> {
   let summary = "Optimized MATMUL(TRANSPOSE(...), ...)";
   let description = [{
     Matrix multiplication where the left hand side is transposed
   }];
 
   let arguments = (ins
-    AnyFortranNumericalOrLogicalArrayObject:$lhs,
-    AnyFortranNumericalOrLogicalArrayObject:$rhs,
+    Arg<AnyFortranNumericalOrLogicalArrayObject, "", [MemRead]>:$lhs,
+    Arg<AnyFortranNumericalOrLogicalArrayObject, "", [MemRead]>:$rhs,
     DefaultValuedAttr<Arith_FastMathAttr,
                       "::mlir::arith::FastMathFlags::none">:$fastmath
   );
@@ -581,8 +606,14 @@
   let hasVerifier = 1;
 }
 
+// this needs a read effect on the source argument because it can generate
+// a fir.load when the source is polymorphic
+// An allocation effect is needed because the value produced by the associate
+// is "deallocated" by hlfir.end_associate (the end_associate must not be
+// removed, and there must be only one hlfir.end_associate).
 def hlfir_AssociateOp : hlfir_Op<"associate", [AttrSizedOperandSegments,
-    DeclareOpInterfaceMethods<fir_FortranVariableOpInterface>]> {
+    DeclareOpInterfaceMethods<fir_FortranVariableOpInterface>,
+    MemoryEffects<[MemAlloc]>]> {
   let summary = "Create a variable from an expression value";
   let description = [{
     Create a variable from an expression value.
@@ -592,7 +623,7 @@
   }];
 
   let arguments = (ins
-    AnyFortranValue:$source,
+    Arg<AnyFortranValue, "", [MemRead]>:$source,
     Optional<AnyShapeOrShiftType>:$shape,
     Variadic<AnyIntegerType>:$typeparams,
     Builtin_StringAttr:$uniq_name,
@@ -635,7 +666,7 @@
   }];
 }
 
-def hlfir_EndAssociateOp : hlfir_Op<"end_associate", []> {
+def hlfir_EndAssociateOp : hlfir_Op<"end_associate", [MemoryEffects<[MemFree]>]> {
   let summary = "Mark the end of life of a variable associated to an expression";
 
   let description = [{
@@ -652,7 +683,9 @@
   let builders = [OpBuilder<(ins "hlfir::AssociateOp":$associate)>];
 }
 
-def hlfir_AsExprOp : hlfir_Op<"as_expr", []> {
+// Allocation effect is because this creates a hlfir.expr, which must be
+// destroyed (only once)
+def hlfir_AsExprOp : hlfir_Op<"as_expr", [MemoryEffects<[MemAlloc]>]> {
   let summary = "Take the value of an array, character or derived variable";
 
   let description = [{
@@ -669,7 +702,7 @@
     hlfir.expr value without paying the price of introducing a copy.
   }];
 
-  let arguments = (ins AnyFortranVariable:$var,
+  let arguments = (ins Arg<AnyFortranVariable, "", [MemRead]>:$var,
                        Optional<I1>:$must_free);
   let results = (outs hlfir_ExprType);
 
@@ -928,7 +961,7 @@
   let assemblyFormat = "$expr attr-dict `:` qualified(type($expr))";
 }
 
-def hlfir_CopyInOp : hlfir_Op<"copy_in", []> {
+def hlfir_CopyInOp : hlfir_Op<"copy_in", [MemoryEffects<[MemAlloc]>]> {
   let summary = "copy a variable into a contiguous temporary if it is not contiguous";
   let description = [{
     Copy a variable into a contiguous temporary if the variable is not
@@ -948,7 +981,7 @@
     is true and, when it is false, the original value will be returned instead.
   }];
 
-  let arguments = (ins fir_BaseBoxType:$var,
+  let arguments = (ins Arg<fir_BaseBoxType, "", [MemRead]>:$var,
                    Optional<I1>:$var_is_present);
 
   let results = (outs fir_BaseBoxType, I1);
@@ -975,7 +1008,7 @@
   }];
 }
 
-def hlfir_CopyOutOp : hlfir_Op<"copy_out", []> {
+def hlfir_CopyOutOp : hlfir_Op<"copy_out", [MemoryEffects<[MemFree]>]> {
   let summary = "copy out a variable after a copy in";
   let description = [{
     If the variable was copied in a temporary in the related hlfir.copy_in,
@@ -988,7 +1021,7 @@
 
   let arguments = (ins fir_BaseBoxType:$temp,
                        I1:$was_copied,
-                       Optional<fir_BaseBoxType>:$var);
+                       Arg<Optional<fir_BaseBoxType>, "", [MemWrite]>:$var);
 
   let assemblyFormat = [{
     $temp `,` $was_copied (`to` $var^)?
@@ -1540,7 +1573,9 @@
   let hasCanonicalizeMethod = 1;
 }
 
-def hlfir_CharExtremumOp : hlfir_Op<"char_extremum", []> {
+// Allocation effect because this creates a hlfir.expr, which must be destroyed
+// (only once)
+def hlfir_CharExtremumOp : hlfir_Op<"char_extremum", [MemoryEffects<[MemAlloc]>]> {
   let summary = "Find max/min from given character strings";
   let description = [{
     Find the lexicographical minimum or maximum of two or more character 
@@ -1551,7 +1586,7 @@
   }];
 
   let arguments = (ins hlfir_CharExtremumPredicateAttr:$predicate,
-                  Variadic<AnyScalarCharacterEntity>:$strings
+                  Arg<Variadic<AnyScalarCharacterEntity>, "", [MemRead]>:$strings
   );
 
   let results = (outs AnyScalarCharacterExpr);
diff --git a/flang/test/HLFIR/memory-effects.fir b/flang/test/HLFIR/memory-effects.fir
new file mode 100644
--- /dev/null
+++ b/flang/test/HLFIR/memory-effects.fir
@@ -0,0 +1,13 @@
+// RUN: fir-opt %s --test-side-effects --verify-diagnostics
+
+func.func @concat(%arg0: !fir.ref<!fir.char<1,10>>, %arg1: !fir.ref<!fir.char<1, 20>>) {
+// expected-remark@+1 {{operation has no memory effects}}
+  %c30 = arith.constant 30 : index
+// expected-remark@+2 {{found an instance of 'allocate' on resource '<Default>'}}
+// expected-remark@+1 {{found an instance of 'read' on a value, on resource '<Default>'}}
+  %0 = hlfir.concat %arg0, %arg1 len %c30 : (!fir.ref<!fir.char<1,10>>, !fir.ref<!fir.char<1,20>>, index) -> (!hlfir.expr<!fir.char<1,30>>)
+// expected-remark@+1 {{operation has no memory effects}}
+  return
+}
+
+// TODO: testing for other operations
diff --git a/flang/test/HLFIR/order_assignments/where-scheduling.f90 b/flang/test/HLFIR/order_assignments/where-scheduling.f90
--- a/flang/test/HLFIR/order_assignments/where-scheduling.f90
+++ b/flang/test/HLFIR/order_assignments/where-scheduling.f90
@@ -139,12 +139,9 @@
 !CHECK-NEXT: run 2 evaluate: where/region_assign1
 !CHECK-NEXT: run 3 evaluate: where/region_assign2
 !CHECK-LABEL: ------------ scheduling where in _QPrhs_lhs_conflict ------------
-!CHECK-NEXT: unknown effect: %{{.*}} = hlfir.transpose %{{.*}} : (!fir.box<!fir.array<?x?xf32>>) -> !hlfir.expr<?x?xf32>
-!CHECK-NEXT: conflict: R/W: %6 = hlfir.designate %{{.*}} (%{{.*}}, %{{.*}})  : (!fir.box<!fir.array<?x?xf32>>, index, index) -> !fir.ref<f32> W:<unknown>
-!CHECK-NEXT: run 1 save    : where/mask
-!CHECK-NEXT: unknown effect: %{{.*}} = hlfir.transpose %{{.*}} : (!fir.box<!fir.array<?x?xf32>>) -> !hlfir.expr<?x?xf32>
-!CHECK-NEXT: run 2 save  (w): where/region_assign1/rhs
-!CHECK-NEXT: run 3 evaluate: where/region_assign1
+!CHECK-NEXT: conflict: R/W: <block argument> of type '!fir.box<!fir.array<?x?xf32>>' at index: 0 W:<block argument> of type '!fir.box<!fir.array<?x?xf32>>' at index: 0
+!CHECK-NEXT: run 1 save    : where/region_assign1/rhs
+!CHECK-NEXT: run 2 evaluate: where/region_assign1
 !CHECK-LABEL: ------------ scheduling where in _QPwhere_construct_no_conflict ------------
 !CHECK-NEXT: run 1 evaluate: where/region_assign1
 !CHECK-NEXT: run 2 evaluate: where/elsewhere1/region_assign1
diff --git a/flang/tools/fir-opt/CMakeLists.txt b/flang/tools/fir-opt/CMakeLists.txt
--- a/flang/tools/fir-opt/CMakeLists.txt
+++ b/flang/tools/fir-opt/CMakeLists.txt
@@ -6,6 +6,7 @@
 if(FLANG_INCLUDE_TESTS)
   set(test_libs
     FIRTestAnalysis
+    MLIRTestIR
     )
 endif()
 
@@ -35,5 +36,4 @@
   MLIRSupport
   MLIRVectorToLLVM
   MLIROptLib
-
 )
diff --git a/flang/tools/fir-opt/fir-opt.cpp b/flang/tools/fir-opt/fir-opt.cpp
--- a/flang/tools/fir-opt/fir-opt.cpp
+++ b/flang/tools/fir-opt/fir-opt.cpp
@@ -24,6 +24,11 @@
 } // namespace test
 } // namespace fir
 
+// Defined in mlir/test, no pulic header.
+namespace mlir {
+void registerSideEffectTestPasses();
+}
+
 int main(int argc, char **argv) {
   fir::support::registerMLIRPassesForFortranTools();
   fir::registerOptCodeGenPasses();
@@ -31,6 +36,7 @@
   hlfir::registerHLFIRPasses();
 #ifdef FLANG_INCLUDE_TESTS
   fir::test::registerTestFIRAliasAnalysisPass();
+  mlir::registerSideEffectTestPasses();
 #endif
   DialectRegistry registry;
   fir::support::registerDialects(registry);