[llvm][NFC] Factor out cost-model independent inling decision

[mtrofin]

Summary

llvm::getInlineCost starts off by determining whether inlining should
happen or not because of user directives or easily determinable
unviability. This CL refactors this functionality as a reusable API.

[davidxl]

llvm/lib/Analysis/InlineCost.cpp

2116

Fast --> AttributeBased

[mtrofin]

Renamed

[davidxl]

lgtm

[mtrofin]

rebased

[mtrofin]

PTAL - this slipped my attention. Since some time passed since I got the LGTM, I wanted to doublecheck there's no pushback to landing it.

[davidxl]

lgtm

[mtrofin]

another rebase / fix build

[mtrofin]

had to add the GetTLI parameter.

llvm/include/llvm/Analysis/InlineCost.h

 //
 InlineCost
 getInlineCost(CallBase &Call, Function *Callee, const InlineParams &Params,
               TargetTransformInfo &CalleeTTI,
               std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
               Optional<function_ref<BlockFrequencyInfo &(Function &)>> GetBFI,
               ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE);
 
+/// Returns InlineResult::success() if the call site should be always inlined
+/// because of user directives, and the inlining is viable. Returns
+/// InlineResult::failure() if the inlining may never happen because of user
+/// directives or incompatibilities detectable without needing callee traversal.
+/// Otherwise returns None, meaning that inlining should be decided based on
+/// other criteria (e.g. cost modeling).
+Optional<InlineResult>
+getAttributeBasedInliningDecision(CallBase &Call, Function *Callee,
+                                  TargetTransformInfo &CalleeTTI);
+
 /// Minimal filter to detect invalid constructs for inlining.
 InlineResult isInlineViable(Function &Callee);
 } // namespace llvm
 
 #endif

llvm/lib/Analysis/InlineCost.cpp

InlineCost llvm::getInlineCost(
     CallBase &Call, const InlineParams &Params, TargetTransformInfo &CalleeTTI,
     std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
     Optional<function_ref<BlockFrequencyInfo &(Function &)>> GetBFI,
     ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
   return getInlineCost(Call, Call.getCalledFunction(), Params, CalleeTTI,
                        GetAssumptionCache, GetBFI, PSI, ORE);
 }
 
-InlineCost llvm::getInlineCost(
-    CallBase &Call, Function *Callee, const InlineParams &Params,
-    TargetTransformInfo &CalleeTTI,
-    std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
-    Optional<function_ref<BlockFrequencyInfo &(Function &)>> GetBFI,
-    ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
+Optional<InlineResult>
+llvm::getAttributeBasedInliningDecision(CallBase &Call, Function *Callee,
+                                        TargetTransformInfo &CalleeTTI) {
 
   // Cannot inline indirect calls.
   if (!Callee)
-    return llvm::InlineCost::getNever("indirect call");
+    return InlineResult::failure("indirect call");
 
   // Never inline calls with byval arguments that does not have the alloca
   // address space. Since byval arguments can be replaced with a copy to an
   // alloca, the inlined code would need to be adjusted to handle that the
   // argument is in the alloca address space (so it is a little bit complicated
   // to solve).
   unsigned AllocaAS = Callee->getParent()->getDataLayout().getAllocaAddrSpace();
   for (unsigned I = 0, E = Call.arg_size(); I != E; ++I)
     if (Call.isByValArgument(I)) {
       PointerType *PTy = cast<PointerType>(Call.getArgOperand(I)->getType());
       if (PTy->getAddressSpace() != AllocaAS)
-        return llvm::InlineCost::getNever("byval arguments without alloca"
-                                          " address space");
+        return InlineResult::failure("byval arguments without alloca"
     }
 
   // Calls to functions with always-inline attributes should be inlined
   // whenever possible.
   if (Call.hasFnAttr(Attribute::AlwaysInline)) {
     auto IsViable = isInlineViable(*Callee);
     if (IsViable.isSuccess())
-      return llvm::InlineCost::getAlways("always inline attribute");
-    return llvm::InlineCost::getNever(IsViable.getFailureReason());
+      return InlineResult::success();
+    return InlineResult::failure(IsViable.getFailureReason());
   }
 
   // Never inline functions with conflicting attributes (unless callee has
   // always-inline attribute).
   Function *Caller = Call.getCaller();
   if (!functionsHaveCompatibleAttributes(Caller, Callee, CalleeTTI))
-    return llvm::InlineCost::getNever("conflicting attributes");
+    return InlineResult::failure("conflicting attributes");
 
   // Don't inline this call if the caller has the optnone attribute.
   if (Caller->hasOptNone())
-    return llvm::InlineCost::getNever("optnone attribute");
+    return InlineResult::failure("optnone attribute");
 
   // Don't inline a function that treats null pointer as valid into a caller
   // that does not have this attribute.
   if (!Caller->nullPointerIsDefined() && Callee->nullPointerIsDefined())
-    return llvm::InlineCost::getNever("nullptr definitions incompatible");
+    return InlineResult::failure("nullptr definitions incompatible");
 
   // Don't inline functions which can be interposed at link-time.
   if (Callee->isInterposable())
-    return llvm::InlineCost::getNever("interposable");
+    return InlineResult::failure("interposable");
 
   // Don't inline functions marked noinline.
   if (Callee->hasFnAttribute(Attribute::NoInline))
-    return llvm::InlineCost::getNever("noinline function attribute");
+    return InlineResult::failure("noinline function attribute");
 
   // Don't inline call sites marked noinline.
   if (Call.isNoInline())
-    return llvm::InlineCost::getNever("noinline call site attribute");
+    return InlineResult::failure("noinline call site attribute");
+
+  return None;
+}
+
+InlineCost llvm::getInlineCost(
+    CallBase &Call, Function *Callee, const InlineParams &Params,
+    TargetTransformInfo &CalleeTTI,
+    std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
+    Optional<function_ref<BlockFrequencyInfo &(Function &)>> GetBFI,
+    ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE) {
+
+  auto UserDecision =
+      llvm::getAttributeBasedInliningDecision(Call, Callee, CalleeTTI);
+
+  if (UserDecision.hasValue()) {
+    if (UserDecision->isSuccess())
+      return llvm::InlineCost::getAlways("always inline attribute");
+    return llvm::InlineCost::getNever(UserDecision->getFailureReason());
+  }
 
   LLVM_DEBUG(llvm::dbgs() << "      Analyzing call of " << Callee->getName()
-                          << "... (caller:" << Caller->getName() << ")\n");
+                          << "... (caller:" << Call.getCaller()->getName()
+                          << ")\n");
 
   InlineCostCallAnalyzer CA(CalleeTTI, GetAssumptionCache, GetBFI, PSI, ORE,
                             *Callee, Call, Params);
   InlineResult ShouldInline = CA.analyze();
 
   LLVM_DEBUG(CA.dump());
 
   // Check if there was a reason to force inlining or no inlining.