[flang] Zero initialize uninitialized components in saved default init

jeanPerier · jeanPerier · commit d3602a762892 · 2023-09-29T01:44:38.000-07:00
Follow up up of llvm#67693 - Zero initialize uninitialized components of saved derived type entity with a default initial value. - Zero initialize uninitialized storage of common blocks with a member with an initial value. - Zero initialized uninitialized saved equivalence This removes all the cases where fir.global are created with an initial value that results in an undef in LLVM for part of the global, leading in surprising LLVM optimizations at -O2 for Fortran folks that expects there saved variables to be zero initialized if there is no explicit or default initial value.
diff --git a/flang/docs/Extensions.md b/flang/docs/Extensions.md
@@ -101,6 +101,8 @@ end
 * `$` and `@` as legal characters in names
 * Initialization in type declaration statements using `/values/`
 * Saved variables without explicit or default initializers are zero initialized.
+* In a saved entity of a type with a default initializer, components without default
+  values are zero initialized.
 * Kind specification with `*`, e.g. `REAL*4`
 * `DOUBLE COMPLEX` as a synonym for `COMPLEX(KIND(0.D0))` --
   but not when spelled `TYPE(DOUBLECOMPLEX)`.
diff --git a/flang/lib/Lower/ConvertVariable.cpp b/flang/lib/Lower/ConvertVariable.cpp
@@ -352,16 +352,17 @@ static mlir::Value genDefaultInitializerValue(
         componentValue = genDefaultInitializerValue(converter, loc, component,
                                                     componentTy, stmtCtx);
       } else {
-        // Component has no initial value.
-        componentValue = builder.create<fir::UndefOp>(loc, componentTy);
+        // Component has no initial value. Set its bits to zero by extension
+        // to match what is expected because other compilers are doing it.
+        componentValue = builder.create<fir::ZeroOp>(loc, componentTy);
       }
     } else if (const auto *proc{
                    component
                        .detailsIf<Fortran::semantics::ProcEntityDetails>()}) {
       if (proc->init().has_value())
         TODO(loc, "procedure pointer component default initialization");
       else
-        componentValue = builder.create<fir::UndefOp>(loc, componentTy);
+        componentValue = builder.create<fir::ZeroOp>(loc, componentTy);
     }
     assert(componentValue && "must have been computed");
     componentValue = builder.createConvert(loc, componentTy, componentValue);
@@ -890,7 +891,7 @@ static fir::GlobalOp defineGlobalAggregateStore(
   Fortran::lower::createGlobalInitialization(
       builder, global, [&](fir::FirOpBuilder &builder) {
         Fortran::lower::StatementContext stmtCtx;
-        mlir::Value initVal = builder.create<fir::UndefOp>(loc, aggTy);
+        mlir::Value initVal = builder.create<fir::ZeroOp>(loc, aggTy);
         builder.create<fir::HasValueOp>(loc, initVal);
       });
   return global;
@@ -1171,7 +1172,7 @@ static void finalizeCommonBlockDefinition(
   mlir::TupleType commonTy = global.getType().cast<mlir::TupleType>();
   auto initFunc = [&](fir::FirOpBuilder &builder) {
     mlir::IndexType idxTy = builder.getIndexType();
-    mlir::Value cb = builder.create<fir::UndefOp>(loc, commonTy);
+    mlir::Value cb = builder.create<fir::ZeroOp>(loc, commonTy);
     unsigned tupIdx = 0;
     std::size_t offset = 0;
     LLVM_DEBUG(llvm::dbgs() << "block {\n");
diff --git a/flang/test/Lower/array.f90 b/flang/test/Lower/array.f90
@@ -4,7 +4,7 @@
 ! CHECK-DAG: %[[VAL_1:.*]] = arith.constant 1.000000e+00 : f32
 ! CHECK-DAG: %[[VAL_2:.*]] = arith.constant 2.400000e+00 : f32
 ! CHECK-DAG: %[[VAL_3:.*]] = arith.constant 0.000000e+00 : f32
-! CHECK: %[[VAL_4:.*]] = fir.undefined tuple<!fir.array<5x5xf32>>
+! CHECK: %[[VAL_4:.*]] = fir.zero_bits tuple<!fir.array<5x5xf32>>
 ! CHECK: %[[VAL_5:.*]] = fir.undefined !fir.array<5x5xf32>
 ! CHECK: %[[VAL_6:.*]] = fir.insert_on_range %[[VAL_5]], %[[VAL_1]] from (0, 0) to (1, 0) : (!fir.array<5x5xf32>, f32) -> !fir.array<5x5xf32>
 ! CHECK: %[[VAL_7:.*]] = fir.insert_on_range %[[VAL_6]], %[[VAL_3]] from (2, 0) to (4, 0) : (!fir.array<5x5xf32>, f32) -> !fir.array<5x5xf32>
diff --git a/flang/test/Lower/common-block-2.f90 b/flang/test/Lower/common-block-2.f90
@@ -6,12 +6,12 @@
 ! - A common block that is initialized outside of a BLOCK DATA.
 
 ! CHECK-LABEL: fir.global @__BLNK__ : tuple<i32, !fir.array<8xi8>> {
-! CHECK:  %[[undef:.*]] = fir.undefined tuple<i32, !fir.array<8xi8>>
+! CHECK:  %[[undef:.*]] = fir.zero_bits tuple<i32, !fir.array<8xi8>>
 ! CHECK:  %[[init:.*]] = fir.insert_value %[[undef]], %c42{{.*}}, [0 : index] : (tuple<i32, !fir.array<8xi8>>, i32) -> tuple<i32, !fir.array<8xi8>>
 ! CHECK:  fir.has_value %[[init]] : tuple<i32, !fir.array<8xi8>>
 
 ! CHECK-LABEL: fir.global @a_ : tuple<i32, !fir.array<8xi8>> {
-! CHECK:  %[[undef:.*]] = fir.undefined tuple<i32, !fir.array<8xi8>>
+! CHECK:  %[[undef:.*]] = fir.zero_bits tuple<i32, !fir.array<8xi8>>
 ! CHECK:  %[[init:.*]] = fir.insert_value %[[undef]], %c42{{.*}}, [0 : index] : (tuple<i32, !fir.array<8xi8>>, i32) -> tuple<i32, !fir.array<8xi8>>
 ! CHECK:  fir.has_value %[[init]] : tuple<i32, !fir.array<8xi8>>
 
diff --git a/flang/test/Lower/common-block.f90 b/flang/test/Lower/common-block.f90
@@ -6,7 +6,7 @@
 ! CHECK: @with_empty_equiv_ = common global [8 x i8] zeroinitializer
 ! CHECK: @x_ = global { float, float } { float 1.0{{.*}}, float 2.0{{.*}} }
 ! CHECK: @y_ = common global [12 x i8] zeroinitializer
-! CHECK: @z_ = global { i32, [4 x i8], float } { i32 42, [4 x i8] undef, float 3.000000e+00 }
+! CHECK: @z_ = global { i32, [4 x i8], float } { i32 42, [4 x i8] zeroinitializer, float 3.000000e+00 }
 
 ! CHECK-LABEL: _QPs0
 subroutine s0
diff --git a/flang/test/Lower/default-initialization-globals.f90 b/flang/test/Lower/default-initialization-globals.f90
@@ -97,7 +97,7 @@ module tinit
   ! CHECK-DAG: %[[VAL_15:.*]] = arith.constant 66 : i32
   ! CHECK: %[[VAL_16:.*]] = fir.undefined !fir.type<_QMtinitTt1{{.*}}>
   ! CHECK: %[[VAL_17:.*]] = fir.insert_value %[[VAL_16]], %[[VAL_11]], ["i", !fir.type<_QMtinitTt1{{.*}}>] : (!fir.type<_QMtinitTt1{{.*}}>, i32) -> !fir.type<_QMtinitTt1{{.*}}>
-  ! CHECK: %[[VAL_18:.*]] = fir.undefined i32
+  ! CHECK: %[[VAL_18:.*]] = fir.zero_bits i32
   ! CHECK: %[[VAL_19:.*]] = fir.insert_value %[[VAL_17]], %[[VAL_18]], ["j", !fir.type<_QMtinitTt1{{.*}}>] : (!fir.type<_QMtinitTt1{{.*}}>, i32) -> !fir.type<_QMtinitTt1{{.*}}>
   ! CHECK: %[[VAL_20:.*]] = fir.address_of(@_QMtinitEziel) : !fir.ref<!fir.array<100xf32>>
   ! CHECK: %[[VAL_21:.*]] = fir.shape %[[VAL_12]] : (index) -> !fir.shape<1>
@@ -111,12 +111,12 @@ module tinit
   ! CHECK: %[[VAL_28:.*]] = fir.insert_value %[[VAL_27]], %[[VAL_26]], ["z", !fir.type<_QMtinitTt1{{.*}}>] : (!fir.type<_QMtinitTt1{{.*}}>, !fir.box<!fir.ptr<!fir.array<?xf32>>>) -> !fir.type<_QMtinitTt1{{.*}}>
   ! CHECK: %[[VAL_29:.*]] = fir.string_lit "hello     "(10) : !fir.char<1,10>
   ! CHECK: %[[VAL_30:.*]] = fir.insert_value %[[VAL_28]], %[[VAL_29]], ["c1", !fir.type<_QMtinitTt1{{.*}}>] : (!fir.type<_QMtinitTt1{{.*}}>, !fir.char<1,10>) -> !fir.type<_QMtinitTt1{{.*}}>
-  ! CHECK: %[[VAL_31:.*]] = fir.undefined !fir.char<1,10>
+  ! CHECK: %[[VAL_31:.*]] = fir.zero_bits !fir.char<1,10>
   ! CHECK: %[[VAL_32:.*]] = fir.insert_value %[[VAL_30]], %[[VAL_31]], ["c2", !fir.type<_QMtinitTt1{{.*}}>] : (!fir.type<_QMtinitTt1{{.*}}>, !fir.char<1,10>) -> !fir.type<_QMtinitTt1{{.*}}>
   ! CHECK: %[[VAL_33:.*]] = fir.undefined !fir.type<_QMtinitTt0{k:i32}>
   ! CHECK: %[[VAL_34:.*]] = fir.insert_value %[[VAL_33]], %[[VAL_15]], ["k", !fir.type<_QMtinitTt0{k:i32}>] : (!fir.type<_QMtinitTt0{k:i32}>, i32) -> !fir.type<_QMtinitTt0{k:i32}>
   ! CHECK: %[[VAL_35:.*]] = fir.insert_value %[[VAL_32]], %[[VAL_34]], ["somet0", !fir.type<_QMtinitTt1{{.*}}>] : (!fir.type<_QMtinitTt1{{.*}}>, !fir.type<_QMtinitTt0{k:i32}>) -> !fir.type<_QMtinitTt1{{.*}}>
-  ! CHECK: %[[VAL_36:.*]] = fir.undefined !fir.type<_QMtinitTtno_init{k:i32}>
+  ! CHECK: %[[VAL_36:.*]] = fir.zero_bits !fir.type<_QMtinitTtno_init{k:i32}>
   ! CHECK: %[[VAL_37:.*]] = fir.insert_value %[[VAL_35]], %[[VAL_36]], ["sometno_init", !fir.type<_QMtinitTt1{{.*}}>] : (!fir.type<_QMtinitTt1{{.*}}>, !fir.type<_QMtinitTtno_init{k:i32}>) -> !fir.type<_QMtinitTt1{{.*}}>
   ! CHECK: %[[VAL_38:.*]] = fir.insert_value %[[VAL_33]], %[[VAL_14]], ["k", !fir.type<_QMtinitTt0{k:i32}>] : (!fir.type<_QMtinitTt0{k:i32}>, i32) -> !fir.type<_QMtinitTt0{k:i32}>
   ! CHECK: %[[VAL_39:.*]] = fir.insert_value %[[VAL_37]], %[[VAL_38]], ["somet0_2", !fir.type<_QMtinitTt1{{.*}}>] : (!fir.type<_QMtinitTt1{{.*}}>, !fir.type<_QMtinitTt0{k:i32}>) -> !fir.type<_QMtinitTt1{{.*}}>
@@ -129,7 +129,7 @@ module tinit
   ! CHECK: %[[VAL_42:.*]] = arith.constant 66 : i32
   ! CHECK: %[[VAL_43:.*]] = fir.undefined !fir.type<_QMtinitTtextendst0{k:i32,l:i32}>
   ! CHECK: %[[VAL_44:.*]] = fir.insert_value %[[VAL_43]], %[[VAL_42]], ["k", !fir.type<_QMtinitTtextendst0{k:i32,l:i32}>] : (!fir.type<_QMtinitTtextendst0{k:i32,l:i32}>, i32) -> !fir.type<_QMtinitTtextendst0{k:i32,l:i32}>
-  ! CHECK: %[[VAL_45:.*]] = fir.undefined i32
+  ! CHECK: %[[VAL_45:.*]] = fir.zero_bits i32
   ! CHECK: %[[VAL_46:.*]] = fir.insert_value %[[VAL_44]], %[[VAL_45]], ["l", !fir.type<_QMtinitTtextendst0{k:i32,l:i32}>] : (!fir.type<_QMtinitTtextendst0{k:i32,l:i32}>, i32) -> !fir.type<_QMtinitTtextendst0{k:i32,l:i32}>
   ! CHECK: fir.has_value %[[VAL_46]] : !fir.type<_QMtinitTtextendst0{k:i32,l:i32}>
 
diff --git a/flang/test/Lower/equivalence-static-init.f90 b/flang/test/Lower/equivalence-static-init.f90
@@ -8,7 +8,7 @@ module module_without_init
   equivalence(i(1), x)
 end module
 ! CHECK-LABEL: fir.global @_QMmodule_without_initEi : !fir.array<8xi8> {
-  ! CHECK: %0 = fir.undefined !fir.array<8xi8>
+  ! CHECK: %0 = fir.zero_bits !fir.array<8xi8>
   ! CHECK: fir.has_value %0 : !fir.array<8xi8>
 ! CHECK}
 
diff --git a/flang/test/Lower/pointer-default-init.f90 b/flang/test/Lower/pointer-default-init.f90
@@ -21,7 +21,7 @@ module test
   type(t) :: test_module_var
 ! CHECK-LABEL:   fir.global @_QMtestEtest_module_var : !fir.type<_QMtestTt{i:i32,x:!fir.box<!fir.ptr<!fir.array<?xf32>>>}> {
 ! CHECK:  %[[VAL_0:.*]] = fir.undefined !fir.type<_QMtestTt{i:i32,x:!fir.box<!fir.ptr<!fir.array<?xf32>>>}>
-! CHECK:  %[[VAL_1:.*]] = fir.undefined i32
+! CHECK:  %[[VAL_1:.*]] = fir.zero_bits i32
 ! CHECK:  %[[VAL_2:.*]] = fir.field_index i
 ! CHECK:  %[[VAL_3:.*]] = fir.insert_value %[[VAL_0]], %[[VAL_1]]
 ! CHECK:  %[[VAL_4:.*]] = fir.zero_bits !fir.ptr<!fir.array<?xf32>>
@@ -97,7 +97,7 @@ subroutine test_saved_pointer()
 
 ! CHECK-LABEL:   fir.global internal @_QFtest_savedEx : !fir.type<_QMtestTt{i:i32,x:!fir.box<!fir.ptr<!fir.array<?xf32>>>}> {
 ! CHECK:  %[[VAL_0:.*]] = fir.undefined !fir.type<_QMtestTt{i:i32,x:!fir.box<!fir.ptr<!fir.array<?xf32>>>}>
-! CHECK:  %[[VAL_1:.*]] = fir.undefined i32
+! CHECK:  %[[VAL_1:.*]] = fir.zero_bits i32
 ! CHECK:  %[[VAL_2:.*]] = fir.field_index i
 ! CHECK:  %[[VAL_3:.*]] = fir.insert_value %[[VAL_0]], %[[VAL_1]]
 ! CHECK:  %[[VAL_4:.*]] = fir.zero_bits !fir.ptr<!fir.array<?xf32>>
diff --git a/flang/test/Lower/pointer-initial-target-2.f90 b/flang/test/Lower/pointer-initial-target-2.f90
@@ -12,7 +12,7 @@
   common /a/ p
   data p /b/
 ! CHECK-LABEL: fir.global @a_ : tuple<!fir.box<!fir.ptr<f32>>>
-  ! CHECK: %[[undef:.*]] = fir.undefined tuple<!fir.box<!fir.ptr<f32>>>
+  ! CHECK: %[[undef:.*]] = fir.zero_bits tuple<!fir.box<!fir.ptr<f32>>>
   ! CHECK: %[[b:.*]] = fir.address_of(@_QEb) : !fir.ref<f32>
   ! CHECK: %[[box:.*]] = fir.embox %[[b]] : (!fir.ref<f32>) -> !fir.box<f32>
   ! CHECK: %[[rebox:.*]] = fir.rebox %[[box]] : (!fir.box<f32>) -> !fir.box<!fir.ptr<f32>>
@@ -41,7 +41,7 @@ block data bdsnake
   integer, pointer :: p => b
   common /snake/ p, b
 ! CHECK-LABEL: fir.global @snake_ : tuple<!fir.box<!fir.ptr<i32>>, i32>
-  ! CHECK: %[[tuple0:.*]] = fir.undefined tuple<!fir.box<!fir.ptr<i32>>, i32>
+  ! CHECK: %[[tuple0:.*]] = fir.zero_bits tuple<!fir.box<!fir.ptr<i32>>, i32>
   ! CHECK: %[[snakeAddr:.*]] = fir.address_of(@snake_) : !fir.ref<tuple<!fir.box<!fir.ptr<i32>>, i32>>
   ! CHECK: %[[byteView:.*]] = fir.convert %[[snakeAddr:.*]] : (!fir.ref<tuple<!fir.box<!fir.ptr<i32>>, i32>>) -> !fir.ref<!fir.array<?xi8>>
   ! CHECK: %[[coor:.*]] = fir.coordinate_of %[[byteView]], %c24{{.*}} : (!fir.ref<!fir.array<?xi8>>, index) -> !fir.ref<i8>
