[PPC] Implement `areInlineCompatible` (#126562)

After the default implementation swap from
https://github.com/llvm/llvm-project/pull/117493, where
`areInlineCompatible` checks if the callee features are a subset of
caller features. This is not a safe assumption in general on PPC. We
fallback to check for strict feature set equality for now, and see what
improvements we can make.

2 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp b/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
index c308ec3..26e9b4b 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp
@@ -895,6 +895,20 @@ PPCTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
   return BaseT::getIntrinsicInstrCost(ICA, CostKind);
 }
 
+bool PPCTTIImpl::areInlineCompatible(const Function *Caller,
+                                     const Function *Callee) const {
+  const TargetMachine &TM = getTLI()->getTargetMachine();
+
+  const FeatureBitset &CallerBits =
+      TM.getSubtargetImpl(*Caller)->getFeatureBits();
+  const FeatureBitset &CalleeBits =
+      TM.getSubtargetImpl(*Callee)->getFeatureBits();
+
+  // Check that targets features are exactly the same. We can revisit to see if
+  // we can improve this.
+  return CallerBits == CalleeBits;
+}
+
 bool PPCTTIImpl::areTypesABICompatible(const Function *Caller,
                                        const Function *Callee,
                                        const ArrayRef<Type *> &Types) const {
diff --git a/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.h b/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.h
index 3cb60d7..bf3ddad 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.h
+++ b/llvm/lib/Target/PowerPC/PPCTargetTransformInfo.h
@@ -139,6 +139,8 @@ public:
       bool UseMaskForCond = false, bool UseMaskForGaps = false);
   InstructionCost getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
                                         TTI::TargetCostKind CostKind);
+  bool areInlineCompatible(const Function *Caller,
+                           const Function *Callee) const;
   bool areTypesABICompatible(const Function *Caller, const Function *Callee,
                              const ArrayRef<Type *> &Types) const;
   bool hasActiveVectorLength(unsigned Opcode, Type *DataType,