Value soft float calls as more expensive in the inliner.

Summary: When evaluating floating point instructions in the inliner, ask the TTI whether it is an expensive operation.  By default, it's not an expensive operation.  This keeps the default behavior the same as before.  The ARM TTI has been updated to return back TCC_Expensive for targets which don't have hardware floating point.

Reviewers: chandlerc, echristo

Reviewed By: echristo

Subscribers: t.p.northover, aemerson, llvm-commits

Differential Revision: http://reviews.llvm.org/D6936

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228263 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/IPA/InlineCost.cpp

@@ -907,6 +907,25 @@ bool CallAnalyzer::analyzeBlock(BasicBlock *BB,
     if (isa<ExtractElementInst>(I) || I->getType()->isVectorTy())
       ++NumVectorInstructions;
 
+    // If the instruction is floating point, and the target says this operation is
+    // expensive or the function has the "use-soft-float" attribute, this may
+    // eventually become a library call.  Treat the cost as such.
+    if (I->getType()->isFloatingPointTy()) {
+      bool hasSoftFloatAttr = false;
+
+      // If the function has the "use-soft-float" attribute, mark it as expensive.
+      if (F.hasFnAttribute("use-soft-float")) {
+        Attribute Attr = F.getFnAttribute("use-soft-float");
+        StringRef Val = Attr.getValueAsString();
+        if (Val == "true")
+          hasSoftFloatAttr = true;
+      }
+
+      if (TTI.getFPOpCost(I->getType()) == TargetTransformInfo::TCC_Expensive ||
+          hasSoftFloatAttr)
+        Cost += InlineConstants::CallPenalty;
+    }
+
     // If the instruction simplified to a constant, there is no cost to this
     // instruction. Visit the instructions using our InstVisitor to account for
     // all of the per-instruction logic. The visit tree returns true if we