[X86] Convert esp-relative movs of function arguments into pushes, step 1

This handles the simplest case for mov -> push conversion:
1. x86-32 calling convention, everything is passed through the stack.
2. There is no reserved call frame.
3. Only registers or immediates are pushed, no attempt to combine a mem-reg-mem sequence into a single PUSHmm.

Differential Revision: http://reviews.llvm.org/D6503

llvm-svn: 223757

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86FrameLowering.h b/llvm/lib/Target/X86/X86FrameLowering.h
index 2ee71159c19..ee0ee227cad 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.h
+++ b/llvm/lib/Target/X86/X86FrameLowering.h
@@ -76,6 +76,16 @@ public:
   void eliminateCallFramePseudoInstr(MachineFunction &MF,
                                  MachineBasicBlock &MBB,
                                  MachineBasicBlock::iterator MI) const override;
+
+private:
+  /// convertArgMovsToPushes - This method tries to convert a call sequence
+  /// that uses sub and mov instructions to put the argument onto the stack
+  /// into a series of pushes.
+  /// Returns true if the transformation succeeded, false if not.
+  bool convertArgMovsToPushes(MachineFunction &MF, 
+                              MachineBasicBlock &MBB,
+                              MachineBasicBlock::iterator I, 
+                              uint64_t Amount) const;
 };
 
 } // End llvm namespace