[clang] [CIR] Handle global string literals as char array initializer (PR #144384)

[Andy Kaylor via cfe-commits]

https://github.com/andykaylor updated https://github.com/llvm/llvm-project/pull/144384

>From 815c01f5041c83c1612f49ee8ccda23c8eca16c8 Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akaylor at nvidia.com>
Date: Fri, 13 Jun 2025 16:03:08 -0700
Subject: [PATCH 1/2] [CIR] Handle global string literals as char array
 initializer

This change adds the line of code needed to handle a string literal as an
initializer for a character array.
---
 clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp | 4 ++--
 clang/test/CIR/CodeGen/string-literals.c     | 4 ++++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp b/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp
index c41ab54be09ca..74d2448accc3e 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp
@@ -254,8 +254,8 @@ class ConstExprEmitter
   }
 
   mlir::Attribute VisitStringLiteral(StringLiteral *e, QualType t) {
-    cgm.errorNYI(e->getBeginLoc(), "ConstExprEmitter::VisitStringLiteral");
-    return {};
+    // This is a string literal initializing an array in an initializer.
+    return cgm.getConstantArrayFromStringLiteral(e);
   }
 
   mlir::Attribute VisitObjCEncodeExpr(ObjCEncodeExpr *e, QualType t) {
diff --git a/clang/test/CIR/CodeGen/string-literals.c b/clang/test/CIR/CodeGen/string-literals.c
index 00f59b09400c8..82dd8395379a7 100644
--- a/clang/test/CIR/CodeGen/string-literals.c
+++ b/clang/test/CIR/CodeGen/string-literals.c
@@ -5,6 +5,10 @@
 // RUN: %clang_cc1 -triple aarch64-none-linux-android21 -emit-llvm %s -o %t.ll
 // RUN: FileCheck --check-prefix=OGCG --input-file=%t.ll %s
 
+char g_str[] = "1234";
+
+// CIR: cir.global external @g_str = #cir.const_array<"1234\00" : !cir.array<!s8i x 5>> : !cir.array<!s8i x 5>
+
 // CIR: cir.global "private" cir_private dsolocal @[[STR1_GLOBAL:.*]] = #cir.const_array<"1\00" : !cir.array<!s8i x 2>> : !cir.array<!s8i x 2>
 // CIR: cir.global "private" cir_private dsolocal @[[STR2_GLOBAL:.*]] = #cir.zero : !cir.array<!s8i x 1>
 // CIR: cir.global "private" cir_private dsolocal @[[STR3_GLOBAL:.*]] = #cir.zero : !cir.array<!s8i x 2>

>From f82033232763ae76d298cf05e0e6eef257d7ff97 Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akaylor at nvidia.com>
Date: Tue, 17 Jun 2025 11:29:16 -0700
Subject: [PATCH 2/2] Add more test cases

---
 clang/test/CIR/CodeGen/string-literals.c   |  8 ++++++++
 clang/test/CIR/CodeGen/string-literals.cpp | 23 ++++++++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 clang/test/CIR/CodeGen/string-literals.cpp

diff --git a/clang/test/CIR/CodeGen/string-literals.c b/clang/test/CIR/CodeGen/string-literals.c
index 82dd8395379a7..90ea21906f363 100644
--- a/clang/test/CIR/CodeGen/string-literals.c
+++ b/clang/test/CIR/CodeGen/string-literals.c
@@ -9,6 +9,14 @@ char g_str[] = "1234";
 
 // CIR: cir.global external @g_str = #cir.const_array<"1234\00" : !cir.array<!s8i x 5>> : !cir.array<!s8i x 5>
 
+char g_oversized[100] = "123";
+
+// CIR: cir.global external @g_oversized = #cir.const_array<"123" : !cir.array<!s8i x 3>, trailing_zeros> : !cir.array<!s8i x 100>
+
+char g_exact[4] = "123";
+
+// CIR: cir.global external @g_exact = #cir.const_array<"123\00" : !cir.array<!s8i x 4>> : !cir.array<!s8i x 4>
+
 // CIR: cir.global "private" cir_private dsolocal @[[STR1_GLOBAL:.*]] = #cir.const_array<"1\00" : !cir.array<!s8i x 2>> : !cir.array<!s8i x 2>
 // CIR: cir.global "private" cir_private dsolocal @[[STR2_GLOBAL:.*]] = #cir.zero : !cir.array<!s8i x 1>
 // CIR: cir.global "private" cir_private dsolocal @[[STR3_GLOBAL:.*]] = #cir.zero : !cir.array<!s8i x 2>
diff --git a/clang/test/CIR/CodeGen/string-literals.cpp b/clang/test/CIR/CodeGen/string-literals.cpp
new file mode 100644
index 0000000000000..c56eb74387329
--- /dev/null
+++ b/clang/test/CIR/CodeGen/string-literals.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -triple aarch64-none-linux-android21 -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
+// RUN: %clang_cc1 -triple aarch64-none-linux-android21 -fclangir -emit-llvm %s -o %t-cir.ll
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t-cir.ll %s
+// RUN: %clang_cc1 -triple aarch64-none-linux-android21 -emit-llvm %s -o %t.ll
+// RUN: FileCheck --check-prefix=OGCG --input-file=%t.ll %s
+
+// CIR: cir.global "private" cir_private dsolocal @[[STR1_GLOBAL:.*]] = #cir.const_array<"abcd\00" : !cir.array<!s8i x 5>> : !cir.array<!s8i x 5>
+
+// LLVM: @[[STR1_GLOBAL:.*]] = private global [5 x i8] c"abcd\00"
+
+// OGCG: @[[STR1_GLOBAL:.*]] = private unnamed_addr constant [5 x i8] c"abcd\00"
+
+decltype(auto) returns_literal() {
+    return "abcd";
+}
+
+// CIR: cir.func{{.*}} @_Z15returns_literalv() -> !cir.ptr<!cir.array<!s8i x 5>>
+// CIR:   %[[RET_ADDR:.*]] = cir.alloca !cir.ptr<!cir.array<!s8i x 5>>, !cir.ptr<!cir.ptr<!cir.array<!s8i x 5>>>, ["__retval"]
+// CIR:   %[[STR_ADDR:.*]] = cir.get_global @[[STR1_GLOBAL]] : !cir.ptr<!cir.array<!s8i x 5>>
+// CIR:   cir.store{{.*}} %[[STR_ADDR]], %[[RET_ADDR]]
+// CIR:   %[[RET:.*]] = cir.load %[[RET_ADDR]]
+// CIR:   cir.return %[[RET]]