Move SPAdj logic from PEI into the targets (NFC)

PEI tries to keep track of how much starting or ending a call sequence adjusts the stack pointer by, so that it can resolve frame-index references. Currently, it takes a very simplistic view of how SP adjustments are done - both FrameStartOpcode and FrameDestroyOpcode adjust it exactly by the amount written in its first argument.

This view is in fact incorrect for some targets (e.g. due to stack re-alignment, or because it may want to adjust the stack pointer in multiple steps). However, that doesn't cause breakage, because most targets (the only in-tree exception appears to be 32-bit ARM) rely on being able to simplify the call frame pseudo-instructions earlier, so this code is never hit. 

Moving the computation into TargetInstrInfo allows targets to override the way the adjustment is computed if they need to have a non-zero SPAdj.

Differential Revision: http://reviews.llvm.org/D6863

llvm-svn: 225437

1 files changed, 23 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetInstrInfo.cpp b/llvm/lib/CodeGen/TargetInstrInfo.cpp
index ab45f89a628..98f342cc110 100644
--- a/llvm/lib/CodeGen/TargetInstrInfo.cpp
+++ b/llvm/lib/CodeGen/TargetInstrInfo.cpp
@@ -28,6 +28,7 @@
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetFrameLowering.h"
 #include <cctype>
 using namespace llvm;
 
@@ -644,6 +645,28 @@ isReallyTriviallyReMaterializableGeneric(const MachineInstr *MI,
   return true;
 }
 
+int TargetInstrInfo::getSPAdjust(const MachineInstr *MI) const {
+  const MachineFunction *MF = MI->getParent()->getParent();
+  const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
+  bool StackGrowsDown =
+    TFI->getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
+
+  int FrameSetupOpcode = getCallFrameSetupOpcode();
+  int FrameDestroyOpcode = getCallFrameDestroyOpcode();
+
+  if (MI->getOpcode() != FrameSetupOpcode &&
+      MI->getOpcode() != FrameDestroyOpcode)
+    return 0;
+ 
+  int SPAdj = MI->getOperand(0).getImm();
+
+  if ((!StackGrowsDown && MI->getOpcode() == FrameSetupOpcode) ||
+       (StackGrowsDown && MI->getOpcode() == FrameDestroyOpcode))
+    SPAdj = -SPAdj;
+
+  return SPAdj;
+}
+
 /// isSchedulingBoundary - Test if the given instruction should be
 /// considered a scheduling boundary. This primarily includes labels
 /// and terminators.