[flang] implement Fortran::lower::convertToBox for trivial types

[tblah]

Summary

Note: the FIR: equivalent for this converts the i1 to a fir.logical<4>.
I expect this is a bug in HLFIR expression lowering, but a separate bug
to what is added by this patch.

[jeanPerier]

I am working on this TODO because it is also firing from some IO statement in SPEC and just uploaded a patch that handle the logical case that was indeed the reason I left this a TODO, the type need to be taken from the origin expression. https://reviews.llvm.org/D143421
I took the liberty of adding your test to the patch.

[tblah]

In D143407#4107486, @jeanPerier wrote:

I am working on this TODO because it is also firing from some IO statement in SPEC and just uploaded a patch that handle the logical case that was indeed the reason I left this a TODO, the type need to be taken from the origin expression. https://reviews.llvm.org/D143421
I took the liberty of adding your test to the patch.

Thanks!

flang/lib/Lower/ConvertExprToHLFIR.cpp

hlfir::EntityWithAttributes Fortran::lower::convertExprToHLFIR(
   return HlfirBuilder(loc, converter, symMap, stmtCtx).gen(expr);
 }
 
 fir::BoxValue Fortran::lower::convertToBox(
     mlir::Location loc, Fortran::lower::AbstractConverter &converter,
     hlfir::Entity entity, Fortran::lower::StatementContext &stmtCtx) {
   auto exv = Fortran::lower::translateToExtendedValue(
       loc, converter.getFirOpBuilder(), entity, stmtCtx);
-  if (fir::isa_trivial(fir::getBase(exv).getType()))
-    TODO(loc, "place trivial in memory");
-  return fir::factory::createBoxValue(converter.getFirOpBuilder(), loc, exv);
+  mlir::Value base = fir::getBase(exv);
+  fir::FirOpBuilder &builder = converter.getFirOpBuilder();
+
+  if (fir::isa_trivial(base.getType())) {
+    // place trivial in memory
+    mlir::Type ty = base.getType();
+    mlir::Operation *op = base.getDefiningOp();
+
+    // put alloca in entry block
+    auto insertPt = builder.saveInsertionPoint();
+    if (auto func = op->getParentOfType<mlir::func::FuncOp>()) {
+      mlir::Block *entryBlock = &func.getBlocks().front();
+      builder.setInsertionPointToStart(entryBlock);
+    }
+    mlir::Value ref = builder.create<fir::AllocaOp>(loc, ty);
+    builder.restoreInsertionPoint(insertPt);
+
+    builder.create<fir::StoreOp>(loc, base, ref);
+    exv = fir::ExtendedValue{ref};
+  }
+
+  return fir::factory::createBoxValue(builder, loc, exv);
 }
 fir::BoxValue Fortran::lower::convertExprToBox(
     mlir::Location loc, Fortran::lower::AbstractConverter &converter,
     const Fortran::lower::SomeExpr &expr, Fortran::lower::SymMap &symMap,
     Fortran::lower::StatementContext &stmtCtx) {
   hlfir::EntityWithAttributes loweredExpr =
       HlfirBuilder(loc, converter, symMap, stmtCtx).gen(expr);
   return convertToBox(loc, converter, loweredExpr, stmtCtx);

flang/test/Lower/HLFIR/intrinsic-subroutines.f90

 ! Test lowering of intrinsic subroutines to HLFIR what matters here
 ! is not to test each subroutine, but to check how their
 ! lowering interfaces with the rest of lowering.
 ! RUN: bbc -emit-fir -hlfir -o - %s | FileCheck %s
 
 subroutine test_subroutine(x)
  real :: x
  call cpu_time(x)
 end subroutine
 ! CHECK-LABEL: func.func @_QPtest_subroutine(
 ! CHECK:  %[[VAL_1:.*]]:2 = hlfir.declare %{{.*}}
 ! CHECK:  %[[VAL_2:.*]] = fir.call @_FortranACpuTime() fastmath<contract> : () -> f64
 ! CHECK:  %[[VAL_3:.*]] = fir.convert %[[VAL_2]] : (f64) -> f32
 ! CHECK:  fir.store %[[VAL_3]] to %[[VAL_1]]#1 : !fir.ref<f32>
+
+! check we can box a trivial value
+subroutine sumMask(s, a)
+  integer :: s
+  integer :: a(:)
+  s = sum(a, mask=.true.)
+endsubroutine
+! CHECK-LABEL: func.func @_QPsummask(
+! CHECK:      %[[ALLOC:.*]] = fir.alloca i1
+! CHECK:      %[[TRUE:.*]] = arith.constant true
+! CHECK-NEXT: fir.store %[[TRUE]] to %[[ALLOC]]
+! CHECK-NEXT: %[[BOX:.*]] = fir.embox %[[ALLOC]] : (!fir.ref<i1>) -> !fir.box<i1>