[WinEH] Insert the catchpad return before CSR restoration

x64 catchpads use rax to inform the unwinder where control should go
next.  However, we must initialize rax before the epilogue sequence so
as to not perturb the unwinder.

llvm-svn: 249910

1 files changed, 21 insertions, 18 deletions

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index f63be63efed..9d20fd7c2a9 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -1058,6 +1058,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
   bool NeedsWinCFI =
       IsWin64Prologue && MF.getFunction()->needsUnwindTableEntry();
   bool IsFunclet = isFuncletReturnInstr(MBBI);
+  MachineBasicBlock *RestoreMBB = nullptr;
 
   // Get the number of bytes to allocate from the FrameInfo.
   uint64_t StackSize = MFI->getStackSize();
@@ -1082,7 +1083,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
     }
 
     // For 32-bit, create a new block for the restore code.
-    MachineBasicBlock *RestoreMBB = TargetMBB;
+    RestoreMBB = TargetMBB;
     if (STI.is32Bit()) {
       RestoreMBB = MF.CreateMachineBasicBlock(MBB.getBasicBlock());
       MF.insert(TargetMBB, RestoreMBB);
@@ -1092,23 +1093,6 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
       MBBI->getOperand(0).setMBB(RestoreMBB);
     }
 
-    // Fill EAX/RAX with the address of the target block.
-    unsigned ReturnReg = STI.is64Bit() ? X86::RAX : X86::EAX;
-    if (STI.is64Bit()) {
-      // LEA64r RestoreMBB(%rip), %rax
-      BuildMI(MBB, MBBI, DL, TII.get(X86::LEA64r), ReturnReg)
-          .addReg(X86::RIP)
-          .addImm(0)
-          .addReg(0)
-          .addMBB(RestoreMBB)
-          .addReg(0);
-    } else {
-      // MOV32ri $RestoreMBB, %eax
-      BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri))
-          .addReg(ReturnReg)
-          .addMBB(RestoreMBB);
-    }
-
     // Pop EBP.
     BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::POP64r : X86::POP32r),
             MachineFramePtr)
@@ -1161,6 +1145,25 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
   }
   MachineBasicBlock::iterator FirstCSPop = MBBI;
 
+  if (RestoreMBB) {
+    // Fill EAX/RAX with the address of the target block.
+    unsigned ReturnReg = STI.is64Bit() ? X86::RAX : X86::EAX;
+    if (STI.is64Bit()) {
+      // LEA64r RestoreMBB(%rip), %rax
+      BuildMI(MBB, FirstCSPop, DL, TII.get(X86::LEA64r), ReturnReg)
+          .addReg(X86::RIP)
+          .addImm(0)
+          .addReg(0)
+          .addMBB(RestoreMBB)
+          .addReg(0);
+    } else {
+      // MOV32ri $RestoreMBB, %eax
+      BuildMI(MBB, FirstCSPop, DL, TII.get(X86::MOV32ri))
+          .addReg(ReturnReg)
+          .addMBB(RestoreMBB);
+    }
+  }
+
   if (MBBI != MBB.end())
     DL = MBBI->getDebugLoc();