Enforce default byte alignment in CMABI for LLVM 11+

Starting from LLVM 11, `alloca`/`load`/`store` instructions require an
explicit `align` value. At the same time, commit 5eb2fa4fb7
implies that for non-aligned globals, no `align` argument will be set
for such user instructions.

Since `align 1` is effect-free, use LLVM APIs & IGC's LLVM wrapper
to automatically add `align 1` starting from LLVM 11, while retaining
the old behavior for earlier LLVM versions.

Author: Artem Gindinson

IGC/VectorCompiler/lib/GenXOpts/CMTrans/CMABI.cpp

@@ -403,14 +403,14 @@ void CMABI::LocalizeGlobals(LocalizationInfo &LI) {
 
     Instruction &FirstI = *Fn->getEntryBlock().begin();
     Type *ElemTy = GV->getType()->getElementType();
+    IGCLLVM::Align GVAlign = IGCLLVM::getCorrectAlign(GV->getAlignment());
     AllocaInst *Alloca = new AllocaInst(ElemTy, vc::AddrSpace::Private,
+                                        /*ArraySize=*/nullptr, GVAlign,
                                         GV->getName() + ".local", &FirstI);
 
-    if (GV->getAlignment())
-      Alloca->setAlignment(IGCLLVM::getCorrectAlign(GV->getAlignment()));
-
     if (!isa<UndefValue>(GV->getInitializer()))
-      new StoreInst(GV->getInitializer(), Alloca, &FirstI);
+      new StoreInst(GV->getInitializer(), Alloca, /*isVolatile=*/false,
+                    GVAlign, &FirstI);
 
     vc::DIBuilder::createDbgDeclareForLocalizedGlobal(*Alloca, *GV, FirstI);
 

IGC/VectorCompiler/lib/GenXOpts/CMTrans/CMImpParam.cpp

@@ -147,6 +147,7 @@ SPDX-License-Identifier: MIT
 #include "llvmWrapper/Analysis/CallGraph.h"
 #include "llvmWrapper/IR/DerivedTypes.h"
 #include "llvmWrapper/IR/Function.h"
+#include "llvmWrapper/Support/Alignment.h"
 
 using namespace llvm;
 
@@ -775,7 +776,8 @@ void CMImpParam::replaceWithGlobal(CallInst *CI) {
   GlobalVariable *GV =
       getOrCreateGlobalForIID(CI->getParent()->getParent(), IID);
   LoadInst *Load = new LoadInst(GV->getType()->getPointerElementType(), GV, "",
-                                /* isVolatile */ false, CI);
+                                /* isVolatile */ false,
+                                IGCLLVM::getCorrectAlign(GV->getAlignment()), CI);
   Load->takeName(CI);
   Load->setDebugLoc(CI->getDebugLoc());
   CI->replaceAllUsesWith(Load);
@@ -1151,12 +1153,15 @@ CMImpParam::processKernelParameters(Function *F,
                        "fewer parameters for new function than expected");
     I2->setName(getImplicitArgName(IID));
 
-    if (GlobalsMap.count(IID)) {
+    auto GlobalsMapIt = GlobalsMap.find(IID);
+    if (GlobalsMapIt != GlobalsMap.end()) {
+      GlobalVariable *GV = GlobalsMapIt->second;
       // Also insert a new store at the start of the function to the global
       // variable used for this implicit argument intrinsic if such global is
       // present. There are no global for pseudo intrinsics and sometimes for
       // local ID when it is used only for kernel prologue.
-      new StoreInst(I2, GlobalsMap[IID], &FirstI);
+      new StoreInst(I2, GV, /*isVolatile=*/false,
+                    IGCLLVM::getCorrectAlign(GV->getAlignment()), &FirstI);
     }
 
     // Prepare the kinds that will go into the metadata

IGC/WrapperLLVM/include/llvmWrapper/Support/Alignment.h

@@ -56,13 +56,12 @@ namespace IGCLLVM {
 
     inline Align getCorrectAlign(uint32_t Val)
     {
-        if (Val == 0)
-        {
-            // LLVM Does not accept 0 alignment.
-            // Instead assume byte-align.
-            Val = 1;
-        }
+#if LLVM_VERSION_MAJOR >= 11
+        // llvm::Align does not accept 0 alignment.
+        return llvm::assumeAligned(Val);
+#else
         return Align{ Val };
+#endif
     }
 
     // It is meant for copying alignement.