[clang] [CIR] Upstream PackIndexingExpr for ScalarExpr (PR #146239)

[Amr Hesham via cfe-commits]

https://github.com/AmrDeveloper created https://github.com/llvm/llvm-project/pull/146239

Upstream PackIndexingExpr for ScalarExpr

>From addc4c8be7497ca61f6a78891da1ce7a5fa9ea69 Mon Sep 17 00:00:00 2001
From: AmrDeveloper <amr96 at programmer.net>
Date: Sat, 28 Jun 2025 22:54:55 +0200
Subject: [PATCH] [CIR] Upstream PackIndexingExpr for ScalarExpr

---
 clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp |  4 ++
 clang/test/CIR/CodeGen/pack-indexing.cpp   | 49 ++++++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 clang/test/CIR/CodeGen/pack-indexing.cpp

diff --git a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
index 955bb5ffc4395..c5f54023cbe61 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
@@ -125,6 +125,10 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
     return {};
   }
 
+  mlir::Value VisitPackIndexingExpr(PackIndexingExpr *e) {
+    return Visit(e->getSelectedExpr());
+  }
+
   mlir::Value VisitParenExpr(ParenExpr *pe) { return Visit(pe->getSubExpr()); }
 
   /// Emits the address of the l-value, then loads and returns the result.
diff --git a/clang/test/CIR/CodeGen/pack-indexing.cpp b/clang/test/CIR/CodeGen/pack-indexing.cpp
new file mode 100644
index 0000000000000..8b12b505164f8
--- /dev/null
+++ b/clang/test/CIR/CodeGen/pack-indexing.cpp
@@ -0,0 +1,49 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++2c -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s -check-prefix=CIR
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++2c -fclangir -emit-llvm %s -o %t.ll
+// RUN: FileCheck --input-file=%t.ll %s -check-prefix=LLVM
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++2c -emit-llvm %s -o %t.ll
+// RUN: FileCheck --input-file=%t.ll %s -check-prefix=OGCG
+
+int pack_indexing(auto... p) { return p...[0]; }
+
+// CIR: %[[P_0:.*]] = cir.alloca !s32i, !cir.ptr<!s32i>, ["p", init]
+// CIR: %[[P_1:.*]] = cir.alloca !s32i, !cir.ptr<!s32i>, ["p", init]
+// CIR: %[[P_2:.*]] = cir.alloca !s32i, !cir.ptr<!s32i>, ["p", init]
+// CIR: %[[RET_VAL:.*]] = cir.alloca !s32i, !cir.ptr<!s32i>, ["__retval"]
+// CIR: %[[RESULT:.*]] = cir.load{{.*}} %[[P_0]] : !cir.ptr<!s32i>, !s32i
+// CIR: cir.store %[[RESULT]], %[[RET_VAL]] : !s32i, !cir.ptr<!s32i>
+// CIR: %[[TMP:.*]] = cir.load %[[RET_VAL]] : !cir.ptr<!s32i>, !s32i
+// CIR: cir.return %[[TMP]] : !s32i
+
+// LLVM: %[[P_0:.*]] = alloca i32, i64 1, align 4
+// LLVM: %[[P_1:.*]] = alloca i32, i64 1, align 4
+// LLVM: %[[P_2:.*]] = alloca i32, i64 1, align 4
+// LLVM: %[[RET_VAL:.*]] = alloca i32, i64 1, align 4
+// LLVM: %[[RESULT:.*]] = load i32, ptr %[[P_0]], align 4
+// LLVM: store i32 %[[RESULT]], ptr %[[RET_VAL]], align 4
+// LLVM: %[[TMP:.*]] = load i32, ptr %[[RET_VAL]], align 4
+// LLVM: ret i32 %[[TMP]]
+
+// OGCG-DAG: %[[P_0:.*]] = alloca i32, align 4
+// OGCG-DAG: %[[P_1:.*]] = alloca i32, align 4
+// OGCG-DAG: %[[P_2:.*]] = alloca i32, align 4
+// OGCG-DAG: %[[RESULT:.*]] = load i32, ptr %[[P_0]], align 4
+// OGCG-DAG-NEXT: ret i32 %[[RESULT]]
+
+int foo() { return pack_indexing(1, 2, 3); }
+
+// CIR: %[[RET_VAL:.*]] = cir.alloca !s32i, !cir.ptr<!s32i>, ["__retval"]
+// CIR: %[[RESULT:.*]] = cir.call @_Z13pack_indexingIJiiiEEiDpT_({{.*}}, {{.*}}, {{.*}}) : (!s32i, !s32i, !s32i) -> !s32i
+// CIR: cir.store %[[RESULT]], %[[RET_VAL]] : !s32i, !cir.ptr<!s32i>
+// CIR: %[[TMP:.*]] = cir.load %[[RET_VAL]] : !cir.ptr<!s32i>, !s32i
+// CIR: cir.return %[[TMP]] : !s32i
+
+// LLVM: %[[RET_VAL:.*]] = alloca i32, i64 1, align 4
+// LLVM: %[[RESULT:.*]] = call i32 @_Z13pack_indexingIJiiiEEiDpT_(i32 1, i32 2, i32 3)
+// LLVM: store i32 %[[RESULT]], ptr %[[RET_VAL]], align 4
+// LLVM: %[[TMP:.*]] = load i32, ptr %[[RET_VAL]], align 4
+// LLVM: ret i32 %[[TMP]]
+
+// OGCG-DAG: %[[CALL:.*]] = call noundef i32 @_Z13pack_indexingIJiiiEEiDpT_(i32 noundef 1, i32 noundef 2, i32 noundef 3)
+// OGCG-DAG-NEXT: ret i32 %[[RESULT]]