[clang] [CIR] Give up when we hit a global-view in dense-element-attr lowering (PR #224379)

[Erich Keane via cfe-commits]

https://github.com/erichkeane updated https://github.com/llvm/llvm-project/pull/224379

>From 8389fb37c6e3cd6a26b87849ba36ccbeec598232 Mon Sep 17 00:00:00 2001
From: erichkeane <ekeane at nvidia.com>
Date: Thu, 17 Sep 2026 10:16:28 -0700
Subject: [PATCH] [CIR] Give up when we hit a global-view in dense-element-attr
 lowering

A ptr-to-int conversion can't be converted to an APInt/APFloat, so this
ends up not being able to produce a valid dense element attr.  This
patch makes us 'fall back' to the insert-value version of any potential
dense-elements lowering if there is a global view as one of the values.
---
 clang/lib/CIR/Lowering/LoweringHelpers.cpp    | 20 ++++++++++++++-----
 .../test/CIR/CodeGen/global-address-to-int.c  |  6 ++++++
 .../const-array-bulk-lowering-fallbacks.cir   | 10 ++++++++++
 3 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/clang/lib/CIR/Lowering/LoweringHelpers.cpp b/clang/lib/CIR/Lowering/LoweringHelpers.cpp
index 1dad8beaa4bce..0b64a37cb6bf4 100644
--- a/clang/lib/CIR/Lowering/LoweringHelpers.cpp
+++ b/clang/lib/CIR/Lowering/LoweringHelpers.cpp
@@ -124,7 +124,7 @@ template <> mlir::APFloat getZeroInitFromType(mlir::Type ty) {
 /// \param dimIndex the current dimension we're processing
 /// \param currentIndex the current index in the values array
 template <typename AttrTy, typename StorageTy>
-void convertToDenseElementsAttrImpl(
+bool convertToDenseElementsAttrImpl(
     cir::ConstArrayAttr attr, llvm::SmallVectorImpl<StorageTy> &values,
     const llvm::SmallVectorImpl<int64_t> &currentDims, int64_t dimIndex,
     int64_t currentIndex) {
@@ -136,7 +136,7 @@ void convertToDenseElementsAttrImpl(
       }
       // Remaining slots are trailing zeros; values was zero-initialized.
       currentIndex += attr.getTrailingZerosNum();
-      return;
+      return true;
     }
   }
 
@@ -171,12 +171,18 @@ void convertToDenseElementsAttrImpl(
       continue;
     }
 
+    // A global view can be the result of pointer conversions, so we can't
+    // represent them as an APInt/APFloat.  So give up if we see one.
+    if (auto global = mlir::dyn_cast<cir::GlobalViewAttr>(eltAttr))
+      return false;
+
     llvm_unreachable("unknown element in ConstArrayAttr");
   }
+  return true;
 }
 
 template <typename AttrTy, typename StorageTy>
-mlir::DenseElementsAttr convertToDenseElementsAttr(
+std::optional<mlir::DenseElementsAttr> convertToDenseElementsAttr(
     cir::ConstArrayAttr attr, const llvm::SmallVectorImpl<int64_t> &dims,
     mlir::Type elementType, mlir::Type convertedElementType) {
   unsigned vectorSize = 1;
@@ -184,8 +190,12 @@ mlir::DenseElementsAttr convertToDenseElementsAttr(
     vectorSize *= dim;
   auto values = llvm::SmallVector<StorageTy, 8>(
       vectorSize, getZeroInitFromType<StorageTy>(elementType));
-  convertToDenseElementsAttrImpl<AttrTy>(attr, values, dims, /*currentDim=*/0,
-                                         /*initialIndex=*/0);
+
+  if (!convertToDenseElementsAttrImpl<AttrTy>(attr, values, dims,
+                                              /*currentDim=*/0,
+                                              /*initialIndex=*/0))
+    return std::nullopt;
+
   return mlir::DenseElementsAttr::get(
       mlir::RankedTensorType::get(dims, convertedElementType),
       llvm::ArrayRef(values));
diff --git a/clang/test/CIR/CodeGen/global-address-to-int.c b/clang/test/CIR/CodeGen/global-address-to-int.c
index 3b24941d4c9c4..d6e02a95d5001 100644
--- a/clang/test/CIR/CodeGen/global-address-to-int.c
+++ b/clang/test/CIR/CodeGen/global-address-to-int.c
@@ -20,3 +20,9 @@ unsigned long garr2 = (unsigned long)&arr[2];
 unsigned long gf = (unsigned long)&f;
 // CIR: cir.global external @gf = #cir.global_view<@f> : !u64i
 // LLVM: @gf = global i64 ptrtoint (ptr @f to i64), align 8
+
+long arr_with_addr[] = { 1L, (long)&x };
+// CIR: cir.global external @arr_with_addr =
+// CIR-SAME: #cir.const_array<[#cir.int<1> : !s64i, #cir.global_view<@x> : !s64i]>
+// CIR-SAME: : !cir.array<!s64i x 2>
+// LLVM: @arr_with_addr = global [2 x i64] [i64 1, i64 ptrtoint (ptr @x to i64)]
diff --git a/clang/test/CIR/Lowering/const-array-bulk-lowering-fallbacks.cir b/clang/test/CIR/Lowering/const-array-bulk-lowering-fallbacks.cir
index 0b4a09d179d44..d321ab39e1c3b 100644
--- a/clang/test/CIR/Lowering/const-array-bulk-lowering-fallbacks.cir
+++ b/clang/test/CIR/Lowering/const-array-bulk-lowering-fallbacks.cir
@@ -1,6 +1,7 @@
 // RUN: cir-opt %s --cir-to-llvm -o - | FileCheck %s
 
 !s32i = !cir.int<s, 32>
+!s64i = !cir.int<s, 64>
 !s8i = !cir.int<s, 8>
 !u16i = !cir.int<u, 16>
 !bi33 = !cir.int<s, 33, bitint>
@@ -21,6 +22,11 @@ module attributes {cir.triple = "x86_64-unknown-linux-gnu"} {
       #cir.const_array<[#cir.global_view<@as1> : !cir.ptr<!s32i>]> :
       !cir.array<!cir.ptr<!s32i> x 1>
 
+  cir.global external @int_arr_with_globalview = #cir.const_array<[
+      #cir.int<1> : !s64i,
+      #cir.global_view<@as1> : !s64i
+  ]> : !cir.array<!s64i x 2>
+
   cir.global external @matrix = #cir.const_array<[
       #cir.const_array<[#cir.int<1> : !s32i, #cir.int<2> : !s32i]> : !cir.array<!s32i x 2>,
       #cir.const_array<[#cir.int<3> : !s32i, #cir.int<4> : !s32i]> : !cir.array<!s32i x 2>
@@ -73,6 +79,10 @@ module attributes {cir.triple = "x86_64-unknown-linux-gnu"} {
 // CHECK-LABEL: llvm.mlir.global external @as_mismatch
 // CHECK:       llvm.insertvalue
 
+// CHECK-LABEL: llvm.mlir.global external @int_arr_with_globalview
+// CHECK:       llvm.ptrtoint
+// CHECK:       llvm.insertvalue
+
 // CHECK-LABEL: llvm.mlir.global external @matrix(
 // CHECK-SAME:    dense<