clang/OpenCL: Fix special casing OpenCL in call emission (#138864)

This essentially reverts 1bf1a15.

OpenCL's handling of address spaces has always been a mess, but it's
better than it used to be so this hack appears to be unnecessary now.

None of the code here should really depend on the language or language
address space. The ABI address space to use is already explicit in the
ABIArgInfo, so use that instead of guessing it has anything to do with
LangAS::Default or getASTAllocaAddressSpace.

The below usage of LangAS::Default and getASTAllocaAddressSpace are also
suspect, but appears to be a more involved and separate fix.

Author: arsenm

clang/lib/CodeGen/CGCall.cpp

@@ -5369,7 +5369,6 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
           NeedCopy = true;
         } else if (I->hasLValue()) {
           auto LV = I->getKnownLValue();
-          auto AS = LV.getAddressSpace();
 
           bool isByValOrRef =
               ArgInfo.isIndirectAliased() || ArgInfo.getIndirectByVal();
@@ -5378,17 +5377,9 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
               (LV.getAlignment() < getContext().getTypeAlignInChars(I->Ty))) {
             NeedCopy = true;
           }
-          if (!getLangOpts().OpenCL) {
-            if ((isByValOrRef && (AS != LangAS::Default &&
-                                  AS != CGM.getASTAllocaAddressSpace()))) {
-              NeedCopy = true;
-            }
-          }
-          // For OpenCL even if RV is located in default or alloca address space
-          // we don't want to perform address space cast for it.
-          else if ((isByValOrRef && Addr.getType()->getAddressSpace() !=
-                                        IRFuncTy->getParamType(FirstIRArg)
-                                            ->getPointerAddressSpace())) {
+
+          if (isByValOrRef && Addr.getType()->getAddressSpace() !=
+                                  ArgInfo.getIndirectAddrSpace()) {
             NeedCopy = true;
           }
         }
@@ -5399,6 +5390,10 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
           auto *T = llvm::PointerType::get(
               CGM.getLLVMContext(), CGM.getDataLayout().getAllocaAddrSpace());
 
+          // FIXME: This should not depend on the language address spaces, and
+          // only the contextual values. If the address space mismatches, see if
+          // we can look through a cast to a compatible address space value,
+          // otherwise emit a copy.
           llvm::Value *Val = getTargetHooks().performAddrSpaceCast(
               *this, V, LangAS::Default, CGM.getASTAllocaAddressSpace(), T,
               true);