[llvm] [IR] Require that global value initializers are sized (PR #137358)

[Nikita Popov via llvm-commits]

https://github.com/nikic updated https://github.com/llvm/llvm-project/pull/137358

>From 552847e4f8c73b7847282b03711400fe40547598 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Fri, 25 Apr 2025 18:25:48 +0200
Subject: [PATCH] [IR] Require that global value initializers are sized

While external globals can be unsized, I don't think an
unsized initializer makes sense.

It seems like the backend currently ends up treating this as a
zero-size global. If people want that behavior, they should
declare it as such.
---
 llvm/docs/LangRef.rst                          | 2 +-
 llvm/lib/IR/Verifier.cpp                       | 2 ++
 llvm/test/Verifier/global-initializer-sized.ll | 5 +++++
 llvm/test/Verifier/scalable-global-vars.ll     | 6 +++---
 4 files changed, 11 insertions(+), 4 deletions(-)
 create mode 100644 llvm/test/Verifier/global-initializer-sized.ll

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 4aa81ad971729..377891a14ba93 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -700,7 +700,7 @@ Global Variables
 Global variables define regions of memory allocated at compilation time
 instead of run-time.
 
-Global variable definitions must be initialized.
+Global variable definitions must be initialized with a sized value.
 
 Global variables in other translation units can also be declared, in which
 case they don't have an initializer.
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 28ba944d8ede3..a8d3003c83c34 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -835,6 +835,8 @@ void Verifier::visitGlobalVariable(const GlobalVariable &GV) {
           "Global variable initializer type does not match global "
           "variable type!",
           &GV);
+    Check(GV.getInitializer()->getType()->isSized(),
+          "Global variable initializer must be sized", &GV);
     // If the global has common linkage, it must have a zero initializer and
     // cannot be constant.
     if (GV.hasCommonLinkage()) {
diff --git a/llvm/test/Verifier/global-initializer-sized.ll b/llvm/test/Verifier/global-initializer-sized.ll
new file mode 100644
index 0000000000000..84fee12b98d4b
--- /dev/null
+++ b/llvm/test/Verifier/global-initializer-sized.ll
@@ -0,0 +1,5 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+ at g = global target("opaque") undef
+
+; CHECK: Global variable initializer must be sized
diff --git a/llvm/test/Verifier/scalable-global-vars.ll b/llvm/test/Verifier/scalable-global-vars.ll
index fb9a3067acba9..9df644d5e10f0 100644
--- a/llvm/test/Verifier/scalable-global-vars.ll
+++ b/llvm/test/Verifier/scalable-global-vars.ll
@@ -13,7 +13,7 @@
 
 ; CHECK-NEXT: Globals cannot contain scalable types
 ; CHECK-NEXT: ptr @ScalableVecStructGlobal
- at ScalableVecStructGlobal = global { i32,  <vscale x 4 x i32> } zeroinitializer
+ at ScalableVecStructGlobal = external global { i32,  <vscale x 4 x i32> }
 
 ; CHECK-NEXT: Globals cannot contain scalable types
 ; CHECK-NEXT: ptr @StructTestGlobal
@@ -23,9 +23,9 @@
 ; CHECK-NEXT: Globals cannot contain scalable types
 ; CHECK-NEXT: ptr @StructArrayTestGlobal
 %struct.array.test = type { [2 x <vscale x 1 x double>] }
- at StructArrayTestGlobal = global %struct.array.test zeroinitializer
+ at StructArrayTestGlobal = external global %struct.array.test
 
 ; CHECK-NEXT: Globals cannot contain scalable types
 ; CHECK-NEXT: ptr @StructTargetTestGlobal
 %struct.target.test = type { target("aarch64.svcount"), target("aarch64.svcount") }
- at StructTargetTestGlobal = global %struct.target.test zeroinitializer
+ at StructTargetTestGlobal = external global %struct.target.test