[Inlining] Introduce the function attribute "inline-max-stacksize"

The value of the attribute is a size in bytes. It has the effect of
suppressing inlining of functions whose stacksizes exceed the given value.

Reviewed By: mtrofin

Differential Revision: https://reviews.llvm.org/D129904

1 files changed, 21 insertions, 6 deletions

diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index ebb1f20..0992a4f 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -161,12 +161,21 @@ static cl::opt<bool> DisableGEPConstOperand(
     cl::desc("Disables evaluation of GetElementPtr with constant operands"));
 
 namespace llvm {
+Optional<int> getStringFnAttrAsInt(const Attribute &Attr) {
+  if (Attr.isValid()) {
+    int AttrValue = 0;
+    if (!Attr.getValueAsString().getAsInteger(10, AttrValue))
+      return AttrValue;
+  }
+  return None;
+}
+
 Optional<int> getStringFnAttrAsInt(CallBase &CB, StringRef AttrKind) {
-  Attribute Attr = CB.getFnAttr(AttrKind);
-  int AttrValue;
-  if (Attr.getValueAsString().getAsInteger(10, AttrValue))
-    return None;
-  return AttrValue;
+  return getStringFnAttrAsInt(CB.getFnAttr(AttrKind));
+}
+
+Optional<int> getStringFnAttrAsInt(Function *F, StringRef AttrKind) {
+  return getStringFnAttrAsInt(F->getFnAttribute(AttrKind));
 }
 
 namespace InlineConstants {
@@ -2713,7 +2722,13 @@ InlineResult CallAnalyzer::analyze() {
 
   // If the callee's stack size exceeds the user-specified threshold,
   // do not let it be inlined.
-  if (AllocatedSize > StackSizeThreshold)
+  // The command line option overrides a limit set in the function attributes.
+  size_t FinalStackSizeThreshold = StackSizeThreshold;
+  if (!StackSizeThreshold.getNumOccurrences())
+    if (Optional<int> AttrMaxStackSize = getStringFnAttrAsInt(
+            Caller, InlineConstants::MaxInlineStackSizeAttributeName))
+      FinalStackSizeThreshold = *AttrMaxStackSize;
+  if (AllocatedSize > FinalStackSizeThreshold)
     return InlineResult::failure("stacksize");
 
   return finalizeAnalysis();