From e3d24b45b8f808ec66213e134c4ceda5202fbe31 Mon Sep 17 00:00:00 2001
From: Sami Tolvanen <samitolvanen@google.com>
Date: Wed, 23 Jun 2021 10:09:21 -0700
Subject: [PATCH] ThinLTO: Fix inline assembly references to static functions
 with CFI

Create an internal alias with the original name for static functions
that are renamed in promoteInternals to avoid breaking inline
assembly references to them.

This relands commit 4474958d3a97dede2caa0920f7c4a4dc7aac57d3
with a fix to a use-of-uninitialized-value error that tripped
MemorySanitizer.

Link: https://github.com/ClangBuiltLinux/linux/issues/1354

Reviewed By: nickdesaulniers, pcc

Differential Revision: https://reviews.llvm.org/D104058
---
 llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp      | 10 ++++++++++
 .../cfi-icall-static-inline-asm.ll                    | 19 +++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 llvm/test/Transforms/ThinLTOBitcodeWriter/cfi-icall-static-inline-asm.ll

diff --git a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
index 37329b4..009b6e3 100644
--- a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
+++ b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
@@ -55,6 +55,7 @@ void promoteInternals(Module &ExportM, Module &ImportM, StringRef ModuleId,
       }
     }
 
+    std::string OldName = Name.str();
     std::string NewName = (Name + ModuleId).str();
 
     if (const auto *C = ExportGV.getComdat())
@@ -69,6 +70,15 @@ void promoteInternals(Module &ExportM, Module &ImportM, StringRef ModuleId,
       ImportGV->setName(NewName);
       ImportGV->setVisibility(GlobalValue::HiddenVisibility);
     }
+
+    if (Function *F = dyn_cast<Function>(&ExportGV)) {
+      // Create a local alias with the original name to avoid breaking
+      // references from inline assembly.
+      GlobalAlias *A = GlobalAlias::create(
+          F->getValueType(), F->getAddressSpace(), GlobalValue::InternalLinkage,
+          OldName, F, &ExportM);
+      appendToCompilerUsed(ExportM, A);
+    }
   }
 
   if (!RenamedComdats.empty())
diff --git a/llvm/test/Transforms/ThinLTOBitcodeWriter/cfi-icall-static-inline-asm.ll b/llvm/test/Transforms/ThinLTOBitcodeWriter/cfi-icall-static-inline-asm.ll
new file mode 100644
index 0000000..70f5322
--- /dev/null
+++ b/llvm/test/Transforms/ThinLTOBitcodeWriter/cfi-icall-static-inline-asm.ll
@@ -0,0 +1,19 @@
+; RUN: opt -thinlto-bc -thinlto-split-lto-unit -o - %s | llvm-modextract -b -n 0 -o - | llvm-dis | FileCheck %s
+
+; CHECK: @a = internal alias {{.*}}@a.[[HASH:[0-9a-f]+]]
+
+define void @b() {
+  %f = alloca void ()*, align 8
+  ; CHECK: store{{.*}} @a.[[HASH]],{{.*}} %f
+  store void ()* @a, void ()** %f, align 8
+  ; CHECK: %1 = call void ()* asm sideeffect "leaq a(%rip)
+  %1 = call void ()* asm sideeffect "leaq a(%rip), $0\0A\09", "=r,~{dirflag},~{fpsr},~{flags}"()
+  ret void
+}
+
+; CHECK: define{{.*}} @a.[[HASH]](){{.*}} !type
+define internal void @a() !type !0 {
+  ret void
+}
+
+!0 = !{i64 0, !"typeid1"}
-- 
2.7.4