[llvm] [Attributor] Prevent infinite loop in AAGlobalValueInfoFloating (PR #94941)
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Mon Jun 10 02:07:42 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Ethan Luis McDonough (EthanLuisMcDonough)
<details>
<summary>Changes</summary>
Global variables that reference themselves alongside a function that is called indirectly can cause an infinite loop in `AAGlobalValueInfoFloating`. The recursive reference is continually pushed back into the workload, causing the attributor to hang indefinitely. This patch fixes the issue by preventing the attributor from following a previously visited use.
---
Full diff: https://github.com/llvm/llvm-project/pull/94941.diff
2 Files Affected:
- (modified) llvm/lib/Transforms/IPO/AttributorAttributes.cpp (+1-1)
- (added) llvm/test/Transforms/Attributor/recursive_globals.ll (+24)
``````````diff
diff --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
index 549d03645f939..8c268e3faf177 100644
--- a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -12031,7 +12031,7 @@ struct AAGlobalValueInfoFloating : public AAGlobalValueInfo {
SmallVectorImpl<const Value *> &Worklist) {
Instruction *UInst = dyn_cast<Instruction>(U.getUser());
if (!UInst) {
- Follow = true;
+ Follow = !Uses.contains(&U);
return true;
}
diff --git a/llvm/test/Transforms/Attributor/recursive_globals.ll b/llvm/test/Transforms/Attributor/recursive_globals.ll
new file mode 100644
index 0000000000000..1af6383b063f4
--- /dev/null
+++ b/llvm/test/Transforms/Attributor/recursive_globals.ll
@@ -0,0 +1,24 @@
+; RUN: opt < %s -passes=attributor
+
+ at glob1 = global { ptr, ptr } { ptr @glob1, ptr @fnc1 }
+ at glob2 = global { ptr, ptr } { ptr @glob3, ptr @fnc2 }
+ at glob3 = global { ptr, ptr } { ptr @glob2, ptr @fnc2 }
+
+define internal void @fnc1() {
+ ret void
+}
+
+define internal void @fnc2() {
+ ret void
+}
+
+define internal void @indr_caller(ptr %0) {
+ call void %0()
+ ret void
+}
+
+define void @main() {
+ call void @indr_caller(ptr @fnc1)
+ call void @indr_caller(ptr @fnc2)
+ ret void
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/94941
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