Make constant argument globalisation disabled by default.

This pass can convert local constant arguments into global values, but it can
have negative effects on code that is borderline to non-conforming, where a
constant argument is modified inside the callee - many compilers accept such
code. So, to use this pass, it needs to be enabled explicitly.

To enable in flang-new, use -mmlir --enable-constant-argument-globalisation

Author: Leporacanthicus

flang/include/flang/Tools/CLOptions.inc

@@ -25,6 +25,10 @@
   static llvm::cl::opt<bool> disable##DOName("disable-" DOOption, \
       llvm::cl::desc("disable " DODescription " pass"), llvm::cl::init(false), \
       llvm::cl::Hidden)
+#define EnableOption(EOName, EOOption, EODescription) \
+  static llvm::cl::opt<bool> enable##EOName("enable-" EOOption, \
+      llvm::cl::desc("enable " EODescription " pass"), llvm::cl::init(false), \
+      llvm::cl::Hidden)
 
 /// Shared option in tools to control whether dynamically sized array
 /// allocations should always be on the heap.
@@ -86,8 +90,8 @@ DisableOption(BoxedProcedureRewrite, "boxed-procedure-rewrite",
 
 DisableOption(ExternalNameConversion, "external-name-interop",
     "convert names with external convention");
-DisableOption(ConstantArgumentGlobalisation, "constant-argument-globalisation",
-    "disable the local constants to global constant conversion");
+EnableOption(ConstantArgumentGlobalisation, "constant-argument-globalisation",
+    "enable the local constants to global constant conversion");
 
 using PassConstructor = std::unique_ptr<mlir::Pass>();
 
@@ -272,7 +276,7 @@ inline void createDefaultFIROptimizerPassPipeline(
     // These passes may increase code size.
     pm.addPass(fir::createSimplifyIntrinsics());
     pm.addPass(fir::createAlgebraicSimplificationPass(config));
-    if (!disableConstantArgumentGlobalisation)
+    if (enableConstantArgumentGlobalisation)
       pm.addPass(fir::createConstantArgumentGlobalisationOpt());
   }
 

flang/lib/Optimizer/Transforms/ConstantArgumentGlobalisation.cpp

@@ -134,7 +134,7 @@ class CallOpRewriter : public mlir::OpRewritePattern<fir::CallOp> {
       for (auto a : allocas) {
 	unsigned count = 0;
 
-	for (auto i : a.first->getUsers())
+	for ([[maybe_unused]]auto i : a.first->getUsers())
 	  ++count;
 
 	// If the alloca is only used for a store and the call operand, the

flang/test/Driver/bbc-mlir-pass-pipeline.f90

@@ -32,7 +32,6 @@
 ! CHECK-NEXT: SimplifyRegionLite
 ! CHECK-NEXT: SimplifyIntrinsics
 ! CHECK-NEXT: AlgebraicSimplification
-! CHECK-NEXT: ConstantArgumentGlobalisationOpt
 ! CHECK-NEXT: CSE
 ! CHECK-NEXT:   (S) 0 num-cse'd - Number of operations CSE'd
 ! CHECK-NEXT:   (S) 0 num-dce'd - Number of operations DCE'd

flang/test/Driver/mlir-pass-pipeline.f90

@@ -66,7 +66,6 @@
 ! ALL-NEXT: SimplifyRegionLite
 !  O2-NEXT: SimplifyIntrinsics
 !  O2-NEXT: AlgebraicSimplification
-!  O2-NEXT: ConstantArgumentGlobalisationOpt
 ! ALL-NEXT: CSE
 ! ALL-NEXT:   (S) 0 num-cse'd - Number of operations CSE'd
 ! ALL-NEXT:   (S) 0 num-dce'd - Number of operations DCE'd

flang/test/Fir/basic-program.fir

@@ -66,7 +66,6 @@ func.func @_QQmain() {
 // PASSES-NEXT: SimplifyRegionLite
 // PASSES-NEXT: SimplifyIntrinsics
 // PASSES-NEXT: AlgebraicSimplification
-// PASSES-NEXT: ConstantArgumentGlobalisationOpt
 // PASSES-NEXT: CSE
 // PASSES-NEXT:   (S) 0 num-cse'd - Number of operations CSE'd
 // PASSES-NEXT:   (S) 0 num-dce'd - Number of operations DCE'd

flang/test/Fir/boxproc.fir

@@ -16,7 +16,7 @@
 
 // CHECK-LABEL: define void @_QPtest_proc_dummy_other(ptr
 // CHECK-SAME:              %[[VAL_0:.*]])
-// CHECK:         call void %[[VAL_0]](ptr @{{.*}})
+// CHECK:         call void %[[VAL_0]](ptr %{{.*}})
 
 func.func @_QPtest_proc_dummy() {
   %c0_i32 = arith.constant 0 : i32

flang/test/Lower/character-local-variables.f90

@@ -1,4 +1,6 @@
 ! RUN: bbc -hlfir=false %s -o - | FileCheck %s
+! RUN: bbc -hlfir=false --enable-constant-argument-globalisation %s -o - \
+! RUN:    | FileCheck %s --check-prefix=CHECK-CONST
 
 ! Test lowering of local character variables
 
@@ -116,8 +118,10 @@ subroutine dyn_array_dyn_len_lb(l, n)
 subroutine assumed_length_param(n)
   character(*), parameter :: c(1)=(/"abcd"/)
   integer :: n
-  ! CHECK: %[[tmp:.*]] = fir.address_of(@_global_const_.{{.*}}) : !fir.ref<i64>
-  ! CHECK: fir.call @_QPtake_int(%[[tmp]]) {{.*}}: (!fir.ref<i64>) -> ()
+  ! CHECK: %[[c4:.*]] = arith.constant 4 : i64
+  ! CHECK: fir.store %[[c4]] to %[[tmp:.*]] : !fir.ref<i64>
+  ! CHECK-CONST: %[[tmp:.*]] = fir.address_of(@_global_const_.{{.*}}) : !fir.ref<i64>
+  ! CHECK-CONST: fir.call @_QPtake_int(%[[tmp]]) {{.*}}: (!fir.ref<i64>) -> ()
   call take_int(len(c(n), kind=8))
 end
 

flang/test/Lower/dummy-arguments.f90

@@ -2,7 +2,9 @@
 
 ! CHECK-LABEL: _QQmain
 program test1
-  ! CHECK-DAG: %[[TEN:.*]] = fir.address_of(@_global_const_.{{.*}}) : !fir.ref<i32>
+  ! CHECK-DAG: %[[TMP:.*]] = fir.alloca
+  ! CHECK-DAG: %[[TEN:.*]] = arith.constant
+  ! CHECK: fir.store %[[TEN]] to %[[TMP]]
   ! CHECK-NEXT: fir.call @_QFPfoo
   call foo(10)
 contains

flang/test/Lower/host-associated.f90

@@ -448,10 +448,11 @@ subroutine bar()
 
 ! CHECK-LABEL: func @_QPtest_proc_dummy_other(
 ! CHECK-SAME:           %[[VAL_0:.*]]: !fir.boxproc<() -> ()>) {
+! CHECK:         %[[VAL_1:.*]] = arith.constant 4 : i32
+! CHECK:         %[[VAL_2:.*]] = fir.alloca i32 {adapt.valuebyref}
+! CHECK:         fir.store %[[VAL_1]] to %[[VAL_2]] : !fir.ref<i32>
 ! CHECK:         %[[VAL_3:.*]] = fir.box_addr %[[VAL_0]] : (!fir.boxproc<() -> ()>) -> ((!fir.ref<i32>) -> ())
-! CHECK:         %[[VAL_1:.*]] = fir.address_of(@_global_const_.{{.*}}) : !fir.ref<i32>
-! CHECK:         fir.call %[[VAL_3]](%[[VAL_1]]) {{.*}}: (!fir.ref<i32>) -> ()
-
+! CHECK:         fir.call %[[VAL_3]](%[[VAL_2]]) {{.*}}: (!fir.ref<i32>) -> ()
 ! CHECK:         return
 ! CHECK:       }
 

flang/test/Transforms/constant-argument-globalisation.fir

@@ -1,5 +1,5 @@
-// RUN: fir-opt --constant-argument-globalisation-opt < %s | FileCheck %s
-// RUN: %flang_fc1 -emit-llvm -flang-deprecated-no-hlfir -O2 -mllvm --disable-constant-argument-globalisation -o - %s | FileCheck --check-prefix=DISABLE %s
+// RUN: fir-opt --constant-argument-globalisation-opt  < %s | FileCheck %s
+// RUN: %flang_fc1 -emit-llvm -flang-deprecated-no-hlfir -O2 -o - %s | FileCheck --check-prefix=DISABLE %s
 module {
   func.func @sub1(%arg0: !fir.ref<i32> {fir.bindc_name = "x"}, %arg1: !fir.ref<i32> {fir.bindc_name = "y"}) {
     %0 = fir.alloca i32 {adapt.valuebyref}