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[flang] Apply nocapture attribute to dummy arguments
Apply llvm.nocapture attribute to dummy arguments that do not have the target, asynchronous, volatile, or pointer attributes in a procedure that is not a bind(c). This was discussed in https://discourse.llvm.org/t/applying-the-nocapture-attribute-to-reference-passed-arguments-in-fortran-subroutines/81401
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‎flang/lib/Optimizer/Transforms/FunctionAttr.cpp

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@@ -10,6 +10,8 @@
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/// \file
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/// This is a generic pass for adding attributes to functions.
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//===----------------------------------------------------------------------===//
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#include "flang/Optimizer/Dialect/FIROpsSupport.h"
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#include "flang/Optimizer/Support/InternalNames.h"
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#include "flang/Optimizer/Transforms/Passes.h"
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#include "mlir/Dialect/LLVMIR/LLVMAttrs.h"
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#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
@@ -45,6 +47,25 @@ void FunctionAttrPass::runOnOperation() {
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LLVM_DEBUG(llvm::dbgs() << "Func-name:" << func.getSymName() << "\n");
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llvm::StringRef name = func.getSymName();
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auto deconstructed = fir::NameUniquer::deconstruct(name);
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bool isFromModule = !deconstructed.second.modules.empty();
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if ((isFromModule || !func.isDeclaration()) &&
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!fir::hasBindcAttr(func.getOperation())) {
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llvm::StringRef nocapture = mlir::LLVM::LLVMDialect::getNoCaptureAttrName();
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mlir::UnitAttr unitAttr = mlir::UnitAttr::get(func.getContext());
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for (auto [index, argType] : llvm::enumerate(func.getArgumentTypes())) {
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if (mlir::isa<fir::ReferenceType>(argType) &&
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!fir::isPointerType(argType) &&
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!func.getArgAttr(index, fir::getTargetAttrName()) &&
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!func.getArgAttr(index, fir::getAsynchronousAttrName()) &&
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!func.getArgAttr(index, fir::getVolatileAttrName()))
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func.setArgAttr(index, nocapture, unitAttr);
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}
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}
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mlir::MLIRContext *context = &getContext();
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if (framePointerKind != mlir::LLVM::framePointerKind::FramePointerKind::None)
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func->setAttr("frame_pointer", mlir::LLVM::FramePointerKindAttr::get(

‎flang/test/Transforms/function-attrs.fir

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// RUN: fir-opt --function-attr %s | FileCheck %s
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// If a function has a body and is not bind(c), and if the dummy argument doesn't have the target,
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// asynchronous, volatile, or pointer attribute, then add llvm.nocapture to the dummy argument.
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func.func @_QParg_nocapture(%arg0: !fir.ref<i32> {fir.bindc_name = "tar", fir.target}, %arg1: !fir.ref<i32> {fir.asynchronous, fir.bindc_name = "asynch"}, %arg2: !fir.ref<i32> {fir.bindc_name = "vol", fir.volatile}, %arg3: !fir.ref<!fir.box<!fir.ptr<i32>>> {fir.bindc_name = "ptr"}, %arg4: !fir.ref<i32> {fir.bindc_name = "nocap"}) {
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%0 = fir.dummy_scope : !fir.dscope
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%1 = fir.declare %arg0 dummy_scope %0 {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QFarg_nocaptureEtar"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
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%2 = fir.declare %arg1 dummy_scope %0 {fortran_attrs = #fir.var_attrs<asynchronous>, uniq_name = "_QFarg_nocaptureEasynch"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
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%3 = fir.declare %arg2 dummy_scope %0 {uniq_name = "_QFarg_nocaptureEvol"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
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%4 = fir.declare %arg3 dummy_scope %0 {fortran_attrs = #fir.var_attrs<pointer>, uniq_name = "_QFarg_nocaptureEptr"} : (!fir.ref<!fir.box<!fir.ptr<i32>>>, !fir.dscope) -> !fir.ref<!fir.box<!fir.ptr<i32>>>
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%5 = fir.declare %arg4 dummy_scope %0 {uniq_name = "_QFarg_nocaptureEnocap"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
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return
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}
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// CHECK-LABEL: func.func @_QParg_nocapture(
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// CHECK-SAME: %[[ARG0:.*]]: !fir.ref<i32> {fir.bindc_name = "tar", fir.target},
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// CHECK-SAME: %[[ARG1:.*]]: !fir.ref<i32> {fir.asynchronous, fir.bindc_name = "asynch"},
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// CHECK-SAME: %[[ARG2:.*]]: !fir.ref<i32> {fir.bindc_name = "vol", fir.volatile},
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// CHECK-SAME: %[[ARG3:.*]]: !fir.ref<!fir.box<!fir.ptr<i32>>> {fir.bindc_name = "ptr"},
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// CHECK-SAME: %[[ARG4:.*]]: !fir.ref<i32> {fir.bindc_name = "nocap", llvm.nocapture}) {
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// CHECK: return
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// CHECK-NEXT: }
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func.func @arg_nocapture_bindc(%arg0: !fir.ref<i32> {fir.bindc_name = "tar", fir.target}, %arg1: !fir.ref<i32> {fir.bindc_name = "nocap"}) attributes {fir.bindc_name = "arg_nocapture_bindc", fir.proc_attrs = #fir.proc_attrs<bind_c>} {
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%0 = fir.dummy_scope : !fir.dscope
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%1 = fir.declare %arg0 dummy_scope %0 {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QFarg_nocapture_bindcEtar"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
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%2 = fir.declare %arg1 dummy_scope %0 {uniq_name = "_QFarg_nocapture_bindcEnocap"} : (!fir.ref<i32>, !fir.dscope) -> !fir.ref<i32>
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return
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}
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// CHECK-LABEL: func.func @arg_nocapture_bindc(
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// CHECK-NOT: llvm.nocapture
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// If a function declaration is from a module and is not bind(c), and if the dummy argument doesn't have
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// the target, asynchronous, volatile, or pointer attribute, then add llvm.nocapture to the dummy argument.
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func.func private @_QMarg_modPcheck_args(!fir.ref<i32> {fir.target}, !fir.ref<i32> {fir.asynchronous}, !fir.ref<i32> {fir.volatile}, !fir.ref<!fir.box<!fir.ptr<i32>>>, !fir.ref<i32>, !fir.boxchar<1>, !fir.ref<complex<f32>>)
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// CHECK-LABEL: func.func private @_QMarg_modPcheck_args(
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// CHECK-SAME: !fir.ref<i32> {fir.target},
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// CHECK-SAME: !fir.ref<i32> {fir.asynchronous},
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// CHECK-SAME: !fir.ref<i32> {fir.volatile},
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// CHECK-SAME: !fir.ref<!fir.box<!fir.ptr<i32>>>,
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// CHECK-SAME: !fir.ref<i32> {llvm.nocapture},
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// CHECK-SAME: !fir.boxchar<1>,
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// CHECK-SAME: !fir.ref<complex<f32>> {llvm.nocapture})

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