[flang-commits] [flang] [flang] allow assumed-rank box in fir.alloca (PR #95947)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-flang-fir-hlfir

Author: None (jeanPerier)

<details>
<summary>Changes</summary>

The alloca can be maximized with the maximum number or ranks, which is reasonable (15 currently as per the standard). Introducing a rank based dynamic allocation would complexify alloca hoisting and stack size analysis (this can be revisited if the standard changes to allow more ranks).

No change is needed since this is already reflected in how the fir.box type is translated to LLVM.

---
Full diff: https://github.com/llvm/llvm-project/pull/95947.diff


2 Files Affected:

- (modified) flang/lib/Optimizer/Dialect/FIROps.cpp (-2) 
- (modified) flang/test/Fir/convert-to-llvm.fir (+14) 


``````````diff
diff --git a/flang/lib/Optimizer/Dialect/FIROps.cpp b/flang/lib/Optimizer/Dialect/FIROps.cpp
index ea8a9752eeeee..6cf0dd23fe456 100644
--- a/flang/lib/Optimizer/Dialect/FIROps.cpp
+++ b/flang/lib/Optimizer/Dialect/FIROps.cpp
@@ -272,8 +272,6 @@ mlir::LogicalResult fir::AllocaOp::verify() {
   mlir::Type outType = getType();
   if (!mlir::isa<fir::ReferenceType>(outType))
     return emitOpError("must be a !fir.ref type");
-  if (fir::isa_unknown_size_box(fir::dyn_cast_ptrEleTy(outType)))
-    return emitOpError("cannot allocate !fir.box of unknown rank or type");
   return mlir::success();
 }
 
diff --git a/flang/test/Fir/convert-to-llvm.fir b/flang/test/Fir/convert-to-llvm.fir
index d7059671d3a88..857d5b2ff303c 100644
--- a/flang/test/Fir/convert-to-llvm.fir
+++ b/flang/test/Fir/convert-to-llvm.fir
@@ -1277,6 +1277,20 @@ func.func @alloca_array_with_holes(%0 : index, %1 : index) -> !fir.ref<!fir.arra
 
 // -----
 
+// Test alloca of assumed-rank box
+
+func.func @alloca_assumed_rank_box() -> !fir.ref<!fir.box<!fir.array<*:f32>>> {
+  %a = fir.alloca !fir.box<!fir.array<*:f32>>
+  return %a : !fir.ref<!fir.box<!fir.array<*:f32>>>
+}
+// CHECK-LABEL: llvm.func @alloca_assumed_rank_box
+// CHECK: %[[ONE:.*]] = llvm.mlir.constant(1 : i64) : i64
+// GENERIC: llvm.alloca %[[ONE]] x !llvm.struct<(ptr, i64, i32, i8, i8, i8, i8, array<15 x array<3 x i64>>)> : (i64) -> !llvm.ptr
+// AMDGPU: %[[AA:.*]] = llvm.alloca %[[ONE]] x !llvm.struct<(ptr, i64, i32, i8, i8, i8, i8, array<15 x array<3 x i64>>)> : (i64) -> !llvm.ptr<5>
+// AMDGPU: llvm.addrspacecast %[[AA]] : !llvm.ptr<5> to !llvm.ptr
+
+// -----
+
 // Test `fir.select_case` operation conversion with INTEGER.
 
 func.func @select_case_integer(%arg0: !fir.ref<i32>) -> i32 {

``````````

</details>


https://github.com/llvm/llvm-project/pull/95947