[IR] Reject inlining strictfp alwaysinline callee into non-strictfp caller (#210701)

Commit af0c933eda added a verifier check requiring every strictfp call
site to reside in a strictfp function.
It caused verify error `call site marked strictfp without caller
function marked strictfp` since AlwaysInliner force-inlines strictfp
callees into non-strictfp callers, bypassing checkStrictFP.

47b3b76825 explictly not implemented inlining strictfp function into
non-strictfp function. But the restriction was lost in 8eb6757564.
8eb6757564 was only NFC for the normal inliner pass. It regressed
AlwaysInliner path which bypasses checkStrictFP.

This PR restores the restriction.

---------

Co-authored-by: Jinsong Ji <jinsong.ji@intel.com>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
Co-authored-by: Nikita Popov <github@npopov.com>

llvm/include/llvm/IR/Attributes.h

@@ -1393,6 +1393,11 @@ LLVM_ABI AttributeMask getUBImplyingAttributes();
 LLVM_ABI bool areInlineCompatible(const Function &Caller,
                                   const Function &Callee);
 
+/// \returns Return false if callee is strictfp and caller is not. Return true
+/// otherwise.
+LLVM_ABI bool isStrictFPInlineCompatible(const Function &Caller,
+                                         const Function &Callee);
+
 /// Checks  if there are any incompatible function attributes between
 /// \p A and \p B.
 ///

llvm/lib/Analysis/InlineCost.cpp

@@ -3210,6 +3210,9 @@ std::optional<InlineResult> llvm::getAttributeBasedInliningDecision(
     if (Call.getAttributes().hasFnAttr(Attribute::NoInline))
       return InlineResult::failure("noinline call site attribute");
 
+    if (!AttributeFuncs::isStrictFPInlineCompatible(*Caller, *Callee))
+      return InlineResult::failure("incompatible strictfp attributes");
+
     auto IsViable = isInlineViable(*Callee);
     if (IsViable.isSuccess())
       return InlineResult::success();

llvm/lib/IR/Attributes.cpp

@@ -2785,6 +2785,11 @@ bool AttributeFuncs::areInlineCompatible(const Function &Caller,
   return hasCompatibleFnAttrs(Caller, Callee);
 }
 
+bool AttributeFuncs::isStrictFPInlineCompatible(const Function &Caller,
+                                                const Function &Callee) {
+  return checkStrictFP(Caller, Callee);
+}
+
 bool AttributeFuncs::areOutlineCompatible(const Function &A,
                                           const Function &B) {
   return hasCompatibleFnAttrs(A, B);

llvm/test/Transforms/Inline/always-inline-strictfp.ll

@@ -0,0 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt -passes=always-inline %s -S | FileCheck %s
+
+; Check strictfp alwaysinline callee isn't inlined into non-strictfp caller.
+
+declare void @foo()
+
+define void @callee() alwaysinline strictfp {
+; CHECK-LABEL: define void @callee(
+; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    call void @foo() #[[ATTR1:[0-9]+]]
+; CHECK-NEXT:    ret void
+;
+entry:
+  call void @foo() strictfp
+  ret void
+}
+
+define void @caller() {
+; CHECK-LABEL: define void @caller() {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    call void @callee()
+; CHECK-NEXT:    ret void
+;
+entry:
+  call void @callee()
+  ret void
+}