[AArch64] FMV support and necessary target features dependencies.

This is Function Multi Versioning (FMV) implementation for AArch64 target in
accordance with Beta Arm C Language Extensions specification
https://github.com/ARM-software/acle/blob/main/main/acle.md#function-multi-versioning
It supports new "target_version" function attribute and extends existing
"target_clones" one. Also missing dependencies for target features were added.

Differential Revision: https://reviews.llvm.org/D127812

1 files changed, 83 insertions, 5 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 874a083..4125730 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -2627,8 +2627,22 @@ void CodeGenFunction::EmitKCFIOperandBundle(
     Bundles.emplace_back("kcfi", CGM.CreateKCFITypeId(FP->desugar()));
 }
 
-llvm::Value *
-CodeGenFunction::FormResolverCondition(const MultiVersionResolverOption &RO) {
+llvm::Value *CodeGenFunction::FormAArch64ResolverCondition(
+    const MultiVersionResolverOption &RO) {
+  llvm::SmallVector<StringRef, 8> CondFeatures;
+  for (const StringRef &Feature : RO.Conditions.Features) {
+    // Form condition for features which are not yet enabled in target
+    if (!getContext().getTargetInfo().hasFeature(Feature))
+      CondFeatures.push_back(Feature);
+  }
+  if (!CondFeatures.empty()) {
+    return EmitAArch64CpuSupports(CondFeatures);
+  }
+  return nullptr;
+}
+
+llvm::Value *CodeGenFunction::FormX86ResolverCondition(
+    const MultiVersionResolverOption &RO) {
   llvm::Value *Condition = nullptr;
 
   if (!RO.Conditions.Architecture.empty())
@@ -2666,8 +2680,72 @@ static void CreateMultiVersionResolverReturn(CodeGenModule &CGM,
 
 void CodeGenFunction::EmitMultiVersionResolver(
     llvm::Function *Resolver, ArrayRef<MultiVersionResolverOption> Options) {
-  assert(getContext().getTargetInfo().getTriple().isX86() &&
-         "Only implemented for x86 targets");
+
+  llvm::Triple::ArchType ArchType =
+      getContext().getTargetInfo().getTriple().getArch();
+
+  switch (ArchType) {
+  case llvm::Triple::x86:
+  case llvm::Triple::x86_64:
+    EmitX86MultiVersionResolver(Resolver, Options);
+    return;
+  case llvm::Triple::aarch64:
+    EmitAArch64MultiVersionResolver(Resolver, Options);
+    return;
+
+  default:
+    assert(false && "Only implemented for x86 and AArch64 targets");
+  }
+}
+
+void CodeGenFunction::EmitAArch64MultiVersionResolver(
+    llvm::Function *Resolver, ArrayRef<MultiVersionResolverOption> Options) {
+  assert(!Options.empty() && "No multiversion resolver options found");
+  assert(Options.back().Conditions.Features.size() == 0 &&
+         "Default case must be last");
+  bool SupportsIFunc = getContext().getTargetInfo().supportsIFunc();
+  assert(SupportsIFunc &&
+         "Multiversion resolver requires target IFUNC support");
+  bool AArch64CpuInitialized = false;
+  llvm::BasicBlock *CurBlock = createBasicBlock("resolver_entry", Resolver);
+
+  for (const MultiVersionResolverOption &RO : Options) {
+    Builder.SetInsertPoint(CurBlock);
+    llvm::Value *Condition = FormAArch64ResolverCondition(RO);
+
+    // The 'default' or 'all features enabled' case.
+    if (!Condition) {
+      CreateMultiVersionResolverReturn(CGM, Resolver, Builder, RO.Function,
+                                       SupportsIFunc);
+      return;
+    }
+
+    if (!AArch64CpuInitialized) {
+      Builder.SetInsertPoint(CurBlock, CurBlock->begin());
+      EmitAArch64CpuInit();
+      AArch64CpuInitialized = true;
+      Builder.SetInsertPoint(CurBlock);
+    }
+
+    llvm::BasicBlock *RetBlock = createBasicBlock("resolver_return", Resolver);
+    CGBuilderTy RetBuilder(*this, RetBlock);
+    CreateMultiVersionResolverReturn(CGM, Resolver, RetBuilder, RO.Function,
+                                     SupportsIFunc);
+    CurBlock = createBasicBlock("resolver_else", Resolver);
+    Builder.CreateCondBr(Condition, RetBlock, CurBlock);
+  }
+
+  // If no default, emit an unreachable.
+  Builder.SetInsertPoint(CurBlock);
+  llvm::CallInst *TrapCall = EmitTrapCall(llvm::Intrinsic::trap);
+  TrapCall->setDoesNotReturn();
+  TrapCall->setDoesNotThrow();
+  Builder.CreateUnreachable();
+  Builder.ClearInsertionPoint();
+}
+
+void CodeGenFunction::EmitX86MultiVersionResolver(
+    llvm::Function *Resolver, ArrayRef<MultiVersionResolverOption> Options) {
 
   bool SupportsIFunc = getContext().getTargetInfo().supportsIFunc();
 
@@ -2678,7 +2756,7 @@ void CodeGenFunction::EmitMultiVersionResolver(
 
   for (const MultiVersionResolverOption &RO : Options) {
     Builder.SetInsertPoint(CurBlock);
-    llvm::Value *Condition = FormResolverCondition(RO);
+    llvm::Value *Condition = FormX86ResolverCondition(RO);
 
     // The 'default' or 'generic' case.
     if (!Condition) {