If -fomit-frame-pointer is used, we still need to record when the %esp register

is modified. Otherwise, the unwinder will get confused. The old code (before I
started my hacking) did this. It dropped on the floor, because I wasn't aware of
this requirement.

On the plus side, if we use "alloca" in a function, we create frame pointers
even with -fomit-frame-pointer is enabled!

This is a Good Thing(tm)!!!

llvm-svn: 75183

1 files changed, 20 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index be4764e2768..c9d3950217b 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -873,7 +873,7 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
     BuildMI(MBB, MBBI, DL, TII.get(X86::DBG_LABEL)).addImm(LabelId);
 
     // Emit DWARF info specifying the offsets of the callee-saved registers.
-    emitCalleeSavedFrameMoves(MF, LabelId, FramePtr);
+    emitCalleeSavedFrameMoves(MF, LabelId, HasFP ? FramePtr : StackPtr);
   }
 
   if (MBBI != MBB.end())
@@ -931,6 +931,25 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
     if (NumBytes)
       emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, TII);
   }
+
+  if (!HasFP && needsFrameMoves && NumBytes) {
+    // Mark end of stack pointer adjustment.
+    unsigned LabelId = MMI->NextLabelID();
+    BuildMI(MBB, MBBI, DL, TII.get(X86::DBG_LABEL)).addImm(LabelId);
+
+    // Define the current CFA rule to use the provided offset.
+    if (StackSize) {
+      MachineLocation SPDst(MachineLocation::VirtualFP);
+      MachineLocation SPSrc(MachineLocation::VirtualFP,
+                            -StackSize + stackGrowth);
+      Moves.push_back(MachineMove(LabelId, SPDst, SPSrc));
+    } else {
+      // FIXME: Verify & implement for FP
+      MachineLocation SPDst(StackPtr);
+      MachineLocation SPSrc(StackPtr, stackGrowth);
+      Moves.push_back(MachineMove(LabelId, SPDst, SPSrc));
+    }
+  }
 }
 
 void X86RegisterInfo::emitEpilogue(MachineFunction &MF,