[flang-commits] [PATCH] D148226: [flang] fix fir.array_coor of fir.box with component references

[Jean Perier via Phabricator via flang-commits]

jeanPerier created this revision.
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When dealing with "derived_array(j)%component" where derived_array
is not a contiguous array, but for which we know the extent, lowering
generates a fir.array_coor op on a !fir.box<!fir.array<cst x T>> with
a fir.slice containing "j" in the component path.

Codegen first computes "derived_array(j)" address using the byte
strides inside the descriptor, and then computes the offset of "j"
from that address with a second GEP.
The type of the address in that second GEP matters since "j" is passed
in the GEP via an index indicating its component position in the type.

The code was using the LLVM type of "derived_array" instead of
"derived_array(j)".
In general, with fir.box, the extent ("cst" above) is unknown and those
types match. But if the extent of "derived_array" is a compile time
constant, its LLVM type will be [cst x T] instead of T*, and the produced
GEP will compute the address of the nth T instead of the nth component
inside T leading to undefined behaviors.

Fix this by computing the element type for the second GEP.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D148226

Files:
  flang/lib/Optimizer/CodeGen/CodeGen.cpp
  flang/test/Fir/array-coor.fir


Index: flang/test/Fir/array-coor.fir
===================================================================
--- flang/test/Fir/array-coor.fir
+++ flang/test/Fir/array-coor.fir
@@ -20,3 +20,26 @@
 // CHECK: %[[t11:.*]] = getelementptr i8, ptr %[[t10]], i64 %[[t8]]
 // CHECK: %[[t12:.*]] = load double, ptr %[[t11]]
 // CHECK: ret double %[[t12]]
+
+func.func @test_array_coor_box_component_slice(%arg0: !fir.box<!fir.array<2x!fir.type<t{i:i32,j:i32}>>>) {
+  %c2 = arith.constant 2 : index
+  %c1 = arith.constant 1 : index
+  %0 = fir.field_index j, !fir.type<t{i:i32,j:i32}>
+  %1 = fir.slice %c1, %c2, %c1 path %0 : (index, index, index, !fir.field) -> !fir.slice<1>
+  %2 = fir.array_coor %arg0 [%1] %c2 : (!fir.box<!fir.array<2x!fir.type<t{i:i32,j:i32}>>>, !fir.slice<1>, index) -> !fir.ref<i32>
+  fir.call @take_int(%2) : (!fir.ref<i32>) -> ()
+  return
+}
+func.func private @take_int(%arg0: !fir.ref<i32>) -> ()
+
+// CHECK-LABEL: define void @test_array_coor_box_component_slice(
+// CHECK-SAME: ptr %[[VAL_0:.*]])
+// CHECK:   %[[VAL_1:.*]] = getelementptr { ptr, i64, i32, i8, i8, i8, i8, [1 x [3 x i64]], ptr, [1 x i64] }, ptr %[[VAL_0]], i32 0, i32 7, i32 0, i32 2
+// CHECK:   %[[VAL_2:.*]] = load i64, ptr %[[VAL_1]]
+// CHECK:   %[[VAL_3:.*]] = mul i64 1, %[[VAL_2]]
+// CHECK:   %[[VAL_4:.*]] = add i64 %[[VAL_3]], 0
+// CHECK:   %[[VAL_5:.*]] = getelementptr { ptr, i64, i32, i8, i8, i8, i8, [1 x [3 x i64]], ptr, [1 x i64] }, ptr %[[VAL_0]], i32 0, i32 0
+// CHECK:   %[[VAL_6:.*]] = load ptr, ptr %[[VAL_5]]
+// CHECK:   %[[VAL_7:.*]] = getelementptr i8, ptr %[[VAL_6]], i64 %[[VAL_4]]
+// CHECK:   %[[VAL_8:.*]] = getelementptr %t, ptr %[[VAL_7]], i32 0, i32 1
+// CHECK:   call void @take_int(ptr %[[VAL_8]])
Index: flang/lib/Optimizer/CodeGen/CodeGen.cpp
===================================================================
--- flang/lib/Optimizer/CodeGen/CodeGen.cpp
+++ flang/lib/Optimizer/CodeGen/CodeGen.cpp
@@ -2448,7 +2448,16 @@
         rewriter.replaceOpWithNewOp<mlir::LLVM::BitcastOp>(coor, ty, addr);
         return mlir::success();
       }
-      auto casted = rewriter.create<mlir::LLVM::BitcastOp>(loc, baseTy, addr);
+      // Cast the element address from void* to the derived type so that the
+      // derived type members can be addresses via a GEP using the index of
+      // components.
+      mlir::Type elementType =
+          baseTy.cast<mlir::LLVM::LLVMPointerType>().getElementType();
+      while (auto arrayTy = elementType.dyn_cast<mlir::LLVM::LLVMArrayType>())
+        elementType = arrayTy.getElementType();
+      mlir::Type elementPtrType = mlir::LLVM::LLVMPointerType::get(elementType);
+      auto casted =
+          rewriter.create<mlir::LLVM::BitcastOp>(loc, elementPtrType, addr);
       args.clear();
       args.push_back(0);
       if (!coor.getLenParams().empty()) {


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