From daceb1ea0fdbe3b113e903df78f6fa6630b6d04f Mon Sep 17 00:00:00 2001
From: Yaxun Liu <Yaxun.Liu@amd.com>
Date: Mon, 14 May 2018 19:20:12 +0000
Subject: CodeGen: Emit string literal in constant address space

Some targets have constant address space (e.g. amdgcn). For them string literal should be
emitted in constant address space then casted to default address space.

Differential Revision: https://reviews.llvm.org/D46643

llvm-svn: 332279
---
 clang/lib/CodeGen/CodeGenModule.cpp | 47 ++++++++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 6 deletions(-)

(limited to 'clang/lib/CodeGen/CodeGenModule.cpp')

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 3a27d999352e..50b653c70ff9 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -3044,6 +3044,39 @@ LangAS CodeGenModule::GetGlobalVarAddressSpace(const VarDecl *D) {
   return getTargetCodeGenInfo().getGlobalVarAddressSpace(*this, D);
 }
 
+LangAS CodeGenModule::getStringLiteralAddressSpace() const {
+  // OpenCL v1.2 s6.5.3: a string literal is in the constant address space.
+  if (LangOpts.OpenCL)
+    return LangAS::opencl_constant;
+  if (auto AS = getTarget().getConstantAddressSpace())
+    return AS.getValue();
+  return LangAS::Default;
+}
+
+// In address space agnostic languages, string literals are in default address
+// space in AST. However, certain targets (e.g. amdgcn) request them to be
+// emitted in constant address space in LLVM IR. To be consistent with other
+// parts of AST, string literal global variables in constant address space
+// need to be casted to default address space before being put into address
+// map and referenced by other part of CodeGen.
+// In OpenCL, string literals are in constant address space in AST, therefore
+// they should not be casted to default address space.
+static llvm::Constant *
+castStringLiteralToDefaultAddressSpace(CodeGenModule &CGM,
+                                       llvm::GlobalVariable *GV) {
+  llvm::Constant *Cast = GV;
+  if (!CGM.getLangOpts().OpenCL) {
+    if (auto AS = CGM.getTarget().getConstantAddressSpace()) {
+      if (AS != LangAS::Default)
+        Cast = CGM.getTargetCodeGenInfo().performAddrSpaceCast(
+            CGM, GV, AS.getValue(), LangAS::Default,
+            GV->getValueType()->getPointerTo(
+                CGM.getContext().getTargetAddressSpace(LangAS::Default)));
+    }
+  }
+  return Cast;
+}
+
 template<typename SomeDecl>
 void CodeGenModule::MaybeHandleStaticInExternC(const SomeDecl *D,
                                                llvm::GlobalValue *GV) {
@@ -4039,10 +4072,8 @@ static llvm::GlobalVariable *
 GenerateStringLiteral(llvm::Constant *C, llvm::GlobalValue::LinkageTypes LT,
                       CodeGenModule &CGM, StringRef GlobalName,
                       CharUnits Alignment) {
-  // OpenCL v1.2 s6.5.3: a string literal is in the constant address space.
-  unsigned AddrSpace = 0;
-  if (CGM.getLangOpts().OpenCL)
-    AddrSpace = CGM.getContext().getTargetAddressSpace(LangAS::opencl_constant);
+  unsigned AddrSpace = CGM.getContext().getTargetAddressSpace(
+      CGM.getStringLiteralAddressSpace());
 
   llvm::Module &M = CGM.getModule();
   // Create a global variable for this string
@@ -4104,7 +4135,9 @@ CodeGenModule::GetAddrOfConstantStringFromLiteral(const StringLiteral *S,
 
   SanitizerMD->reportGlobalToASan(GV, S->getStrTokenLoc(0), "<string literal>",
                                   QualType());
-  return ConstantAddress(GV, Alignment);
+
+  return ConstantAddress(castStringLiteralToDefaultAddressSpace(*this, GV),
+                         Alignment);
 }
 
 /// GetAddrOfConstantStringFromObjCEncode - Return a pointer to a constant
@@ -4148,7 +4181,9 @@ ConstantAddress CodeGenModule::GetAddrOfConstantCString(
                                   GlobalName, Alignment);
   if (Entry)
     *Entry = GV;
-  return ConstantAddress(GV, Alignment);
+
+  return ConstantAddress(castStringLiteralToDefaultAddressSpace(*this, GV),
+                         Alignment);
 }
 
 ConstantAddress CodeGenModule::GetAddrOfGlobalTemporary(
-- 
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