Allow the FP stackifier to completely ignore functions that do not use FP at

all.  This should speed up the X86 backend fairly significantly on integer
codes.  Now if only we didn't have to compute livevar still... ;-)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19796 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86FloatingPoint.cpp b/lib/Target/X86/X86FloatingPoint.cpp
index 30763f0..899f7cd 100644 (file)
--- a/lib/Target/X86/X86FloatingPoint.cpp
+++ b/lib/Target/X86/X86FloatingPoint.cpp
@@ -157,6 +157,21 @@ FunctionPass *llvm::createX86FloatingPointStackifierPass() { return new FPS(); }
 /// register references into FP stack references.
 ///
 bool FPS::runOnMachineFunction(MachineFunction &MF) {
+  // We only need to run this pass if there are any FP registers used in this
+  // function.  If it is all integer, there is nothing for us to do!
+  const bool *PhysRegsUsed = MF.getUsedPhysregs();
+  bool FPIsUsed = false;
+
+  assert(X86::FP6 == X86::FP0+6 && "Register enums aren't sorted right!");
+  for (unsigned i = 0; i <= 6; ++i)
+    if (PhysRegsUsed[X86::FP0+i]) {
+      FPIsUsed = true;
+      break;
+    }
+
+  // Early exit.
+  if (!FPIsUsed) return false;
+
   LV = &getAnalysis<LiveVariables>();
   StackTop = 0;