Cleanup the handling of noinline function attributes, -fno-inline,

-fno-inline-functions, -O0, and optnone.

These were really, really tangled together:
- We used the noinline LLVM attribute for -fno-inline
  - But not for -fno-inline-functions (breaking LTO)
  - But we did use it for -finline-hint-functions (yay, LTO is happy!)
  - But we didn't for -O0 (LTO is sad yet again...)
- We had weird structuring of CodeGenOpts with both an inlining
  enumeration and a boolean. They interacted in weird ways and
  needlessly.
- A *lot* of set smashing went on with setting these, and then got worse
  when we considered optnone and other inlining-effecting attributes.
- A bunch of inline affecting attributes were managed in a completely
  different place from -fno-inline.
- Even with -fno-inline we failed to put the LLVM noinline attribute
  onto many generated function definitions because they didn't show up
  as AST-level functions.
- If you passed -O0 but -finline-functions we would run the normal
  inliner pass in LLVM despite it being in the O0 pipeline, which really
  doesn't make much sense.
- Lastly, we used things like '-fno-inline' to manipulate the pass
  pipeline which forced the pass pipeline to be much more
  parameterizable than it really needs to be. Instead we can *just* use
  the optimization level to select a pipeline and control the rest via
  attributes.

Sadly, this causes a bunch of churn in tests because we don't run the
optimizer in the tests and check the contents of attribute sets. It
would be awesome if attribute sets were a bit more FileCheck friendly,
but oh well.

I think this is a significant improvement and should remove the semantic
need to change what inliner pass we run in order to comply with the
requested inlining semantics by relying completely on attributes. It
also cleans up tho optnone and related handling a bit.

One unfortunate aspect of this is that for generating alwaysinline
routines like those in OpenMP we end up removing noinline and then
adding alwaysinline. I tried a bunch of other approaches, but because we
recompute function attributes from scratch and don't have a declaration
here I couldn't find anything substantially cleaner than this.

Differential Revision: https://reviews.llvm.org/D28053

llvm-svn: 290398

1 files changed, 54 insertions, 25 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 64c2bd673cc..f66cfef7766 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -875,6 +875,13 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
     B.addAttribute(llvm::Attribute::StackProtectReq);
 
   if (!D) {
+    // If we don't have a declaration to control inlining, the function isn't
+    // explicitly marked as alwaysinline for semantic reasons, and inlining is
+    // disabled, mark the function as noinline.
+    if (!F->hasFnAttribute(llvm::Attribute::AlwaysInline) &&
+        CodeGenOpts.getInlining() == CodeGenOptions::OnlyAlwaysInlining)
+      B.addAttribute(llvm::Attribute::NoInline);
+
     F->addAttributes(llvm::AttributeSet::FunctionIndex,
                      llvm::AttributeSet::get(
                          F->getContext(),
@@ -882,7 +889,23 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
     return;
   }
 
-  if (D->hasAttr<NakedAttr>()) {
+  if (D->hasAttr<OptimizeNoneAttr>()) {
+    B.addAttribute(llvm::Attribute::OptimizeNone);
+
+    // OptimizeNone implies noinline; we should not be inlining such functions.
+    B.addAttribute(llvm::Attribute::NoInline);
+    assert(!F->hasFnAttribute(llvm::Attribute::AlwaysInline) &&
+           "OptimizeNone and AlwaysInline on same function!");
+
+    // We still need to handle naked functions even though optnone subsumes
+    // much of their semantics.
+    if (D->hasAttr<NakedAttr>())
+      B.addAttribute(llvm::Attribute::Naked);
+
+    // OptimizeNone wins over OptimizeForSize and MinSize.
+    F->removeFnAttr(llvm::Attribute::OptimizeForSize);
+    F->removeFnAttr(llvm::Attribute::MinSize);
+  } else if (D->hasAttr<NakedAttr>()) {
     // Naked implies noinline: we should not be inlining such functions.
     B.addAttribute(llvm::Attribute::Naked);
     B.addAttribute(llvm::Attribute::NoInline);
@@ -891,41 +914,47 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
   } else if (D->hasAttr<NoInlineAttr>()) {
     B.addAttribute(llvm::Attribute::NoInline);
   } else if (D->hasAttr<AlwaysInlineAttr>() &&
-             !F->getAttributes().hasAttribute(llvm::AttributeSet::FunctionIndex,
-                                              llvm::Attribute::NoInline)) {
+             !F->hasFnAttribute(llvm::Attribute::NoInline)) {
     // (noinline wins over always_inline, and we can't specify both in IR)
     B.addAttribute(llvm::Attribute::AlwaysInline);
+  } else if (CodeGenOpts.getInlining() == CodeGenOptions::OnlyAlwaysInlining) {
+    // If we're not inlining, then force everything that isn't always_inline to
+    // carry an explicit noinline attribute.
+    if (!F->hasFnAttribute(llvm::Attribute::AlwaysInline))
+      B.addAttribute(llvm::Attribute::NoInline);
+  } else {
+    // Otherwise, propagate the inline hint attribute and potentially use its
+    // absence to mark things as noinline.
+    if (auto *FD = dyn_cast<FunctionDecl>(D)) {
+      if (any_of(FD->redecls(), [&](const FunctionDecl *Redecl) {
+            return Redecl->isInlineSpecified();
+          })) {
+        B.addAttribute(llvm::Attribute::InlineHint);
+      } else if (CodeGenOpts.getInlining() ==
+                     CodeGenOptions::OnlyHintInlining &&
+                 !FD->isInlined() &&
+                 !F->hasFnAttribute(llvm::Attribute::AlwaysInline)) {
+        B.addAttribute(llvm::Attribute::NoInline);
+      }
+    }
   }
 
-  if (D->hasAttr<ColdAttr>()) {
-    if (!D->hasAttr<OptimizeNoneAttr>())
+  // Add other optimization related attributes if we are optimizing this
+  // function.
+  if (!D->hasAttr<OptimizeNoneAttr>()) {
+    if (D->hasAttr<ColdAttr>()) {
       B.addAttribute(llvm::Attribute::OptimizeForSize);
-    B.addAttribute(llvm::Attribute::Cold);
-  }
+      B.addAttribute(llvm::Attribute::Cold);
+    }
 
-  if (D->hasAttr<MinSizeAttr>())
-    B.addAttribute(llvm::Attribute::MinSize);
+    if (D->hasAttr<MinSizeAttr>())
+      B.addAttribute(llvm::Attribute::MinSize);
+  }
 
   F->addAttributes(llvm::AttributeSet::FunctionIndex,
                    llvm::AttributeSet::get(
                        F->getContext(), llvm::AttributeSet::FunctionIndex, B));
 
-  if (D->hasAttr<OptimizeNoneAttr>()) {
-    // OptimizeNone implies noinline; we should not be inlining such functions.
-    F->addFnAttr(llvm::Attribute::OptimizeNone);
-    F->addFnAttr(llvm::Attribute::NoInline);
-
-    // OptimizeNone wins over OptimizeForSize, MinSize, AlwaysInline.
-    F->removeFnAttr(llvm::Attribute::OptimizeForSize);
-    F->removeFnAttr(llvm::Attribute::MinSize);
-    assert(!F->hasFnAttribute(llvm::Attribute::AlwaysInline) &&
-           "OptimizeNone and AlwaysInline on same function!");
-
-    // Attribute 'inlinehint' has no effect on 'optnone' functions.
-    // Explicitly remove it from the set of function attributes.
-    F->removeFnAttr(llvm::Attribute::InlineHint);
-  }
-
   unsigned alignment = D->getMaxAlignment() / Context.getCharWidth();
   if (alignment)
     F->setAlignment(alignment);