From c2db4248a9f03ae2e23ef38290efe606a82ce484 Mon Sep 17 00:00:00 2001
From: Tim Besard <tim.besard@gmail.com>
Date: Fri, 11 Sep 2020 17:08:52 +0200
Subject: [PATCH] Don't rewrite global aliases during multiversioning.

Fixes JuliaLang/julia#34064
---
 src/llvm-multiversioning.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/llvm-multiversioning.cpp b/src/llvm-multiversioning.cpp
index 68081eb53d3a5b..8a68d753685835 100644
--- a/src/llvm-multiversioning.cpp
+++ b/src/llvm-multiversioning.cpp
@@ -702,12 +702,16 @@ void CloneCtx::fix_gv_uses()
     auto single_pass = [&] (Function *orig_f) {
         bool changed = false;
         for (auto uses = ConstantUses<GlobalValue>(orig_f, M); !uses.done(); uses.next()) {
-            changed = true;
             auto &stack = uses.get_stack();
             auto info = uses.get_info();
             // We only support absolute pointer relocation.
             assert(info.samebits);
             // And only for non-constant global variable initializers
+            if (isa<GlobalAlias>(info.val)) {
+                // ... but don't crash on global aliases, since we'll retain the original f
+                // (these are emitted for C-callable functions)
+                continue;
+            }
             auto val = cast<GlobalVariable>(info.val);
             assert(info.use->getOperandNo() == 0);
             assert(!val->isConstant());
@@ -717,6 +721,7 @@ void CloneCtx::fix_gv_uses()
                 addr = ConstantExpr::getAdd(addr, ConstantInt::get(T_size, info.offset));
             gv_relocs.emplace_back(addr, fid);
             val->setInitializer(rewrite_gv_init(stack));
+            changed = true;
         }
         return changed;
     };