[flang][debug] Add stride information for assumed shape array. (#106703)

Without this information, debugger could present wrong values for arrays
in certain cases as shown in issue #105646.

Fixes #105646.

Author: abidh

flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp

@@ -116,8 +116,8 @@ mlir::LLVM::DITypeAttr DebugTypeGenerator::convertBoxedSequenceType(
   unsigned offset = dimsOffset;
   const unsigned indexSize = dimsSize / 3;
   for ([[maybe_unused]] auto _ : seqTy.getShape()) {
-    // For each dimension, find the offset of count and lower bound in the
-    // descriptor and generate the dwarf expression to extract it.
+    // For each dimension, find the offset of count, lower bound and stride in
+    // the descriptor and generate the dwarf expression to extract it.
     // FIXME: If `indexSize` happens to be bigger than address size on the
     // system then we may have to change 'DW_OP_deref' here.
     addOp(llvm::dwarf::DW_OP_push_object_address, {});
@@ -139,10 +139,18 @@ mlir::LLVM::DITypeAttr DebugTypeGenerator::convertBoxedSequenceType(
         mlir::LLVM::DIExpressionAttr::get(context, ops);
     ops.clear();
 
+    addOp(llvm::dwarf::DW_OP_push_object_address, {});
+    addOp(llvm::dwarf::DW_OP_plus_uconst,
+          {offset + (indexSize * kDimStridePos)});
+    addOp(llvm::dwarf::DW_OP_deref, {});
+    // stride[i] = *(base_addr + offset + (indexSize * kDimStridePos))
+    mlir::LLVM::DIExpressionAttr strideAttr =
+        mlir::LLVM::DIExpressionAttr::get(context, ops);
+    ops.clear();
+
     offset += dimsSize;
     mlir::LLVM::DISubrangeAttr subrangeTy = mlir::LLVM::DISubrangeAttr::get(
-        context, countAttr, lowerAttr, /*upperBound=*/nullptr,
-        /*stride=*/nullptr);
+        context, countAttr, lowerAttr, /*upperBound=*/nullptr, strideAttr);
     elements.push_back(subrangeTy);
   }
   return mlir::LLVM::DICompositeTypeAttr::get(

flang/test/Integration/debug-assumed-shape-array.f90

@@ -8,6 +8,6 @@ end subroutine ff
 
 ! CHECK-DAG: !DICompositeType(tag: DW_TAG_array_type{{.*}}elements: ![[ELEMS:[0-9]+]], dataLocation: !DIExpression(DW_OP_push_object_address, DW_OP_deref))
 ! CHECK-DAG: ![[ELEMS]] = !{![[ELEM1:[0-9]+]], ![[ELEM2:[0-9]+]]}
-! CHECK-DAG: ![[ELEM1]] = !DISubrange(count: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 32, DW_OP_deref), lowerBound: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 24, DW_OP_deref))
-! CHECK-DAG: ![[ELEM2]] = !DISubrange(count: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 56, DW_OP_deref), lowerBound: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 48, DW_OP_deref))
+! CHECK-DAG: ![[ELEM1]] = !DISubrange(count: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 32, DW_OP_deref), lowerBound: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 24, DW_OP_deref), stride: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 40, DW_OP_deref))
+! CHECK-DAG: ![[ELEM2]] = !DISubrange(count: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 56, DW_OP_deref), lowerBound: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 48, DW_OP_deref), stride: !DIExpression(DW_OP_push_object_address, DW_OP_plus_uconst, 64, DW_OP_deref))
 

flang/test/Transforms/debug-assumed-shape-array.fir

@@ -11,6 +11,6 @@ module attributes {dlti.dl_spec = #dlti.dl_spec<#dlti.dl_entry<i64, dense<64> :
 #loc2 = loc("test1.f90":3:16)
 
 // CHECK: #llvm.di_composite_type<tag = DW_TAG_array_type
-// CHECK-SAME: elements = #llvm.di_subrange<count = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(32), DW_OP_deref]>, lowerBound = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(24), DW_OP_deref]>>,
-// CHECK-SAME: #llvm.di_subrange<count = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(56), DW_OP_deref]>, lowerBound = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(48), DW_OP_deref]>>
+// CHECK-SAME: elements = #llvm.di_subrange<count = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(32), DW_OP_deref]>, lowerBound = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(24), DW_OP_deref]>, stride = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(40), DW_OP_deref]>>,
+// CHECK-SAME: #llvm.di_subrange<count = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(56), DW_OP_deref]>, lowerBound = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(48), DW_OP_deref]>, stride = #llvm.di_expression<[DW_OP_push_object_address, DW_OP_plus_uconst(64), DW_OP_deref]>>
 // CHECK-SAME: dataLocation = <[DW_OP_push_object_address, DW_OP_deref]>>