From 8d335f0c319bd2f9e63a76427eaa80531c21e52f Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Fri, 9 Oct 2015 22:18:45 +0000
Subject: [PATCH] [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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249910 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86FrameLowering.cpp   | 39 ++++++++++++++-------------
 test/CodeGen/X86/win-catchpad-csrs.ll |  3 +++
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index f63be63efed..9d20fd7c2a9 100644
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/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();
 
diff --git a/test/CodeGen/X86/win-catchpad-csrs.ll b/test/CodeGen/X86/win-catchpad-csrs.ll
index 05a59ac9b62..5e8c3350bca 100644
--- a/test/CodeGen/X86/win-catchpad-csrs.ll
+++ b/test/CodeGen/X86/win-catchpad-csrs.ll
@@ -123,6 +123,8 @@ catchendblock:                                    ; preds = %catch,
 ; X64: movq %rdx, 16(%rsp)
 ; X64: pushq %rbp
 ; X64: .seh_pushreg 5
+; X64: pushq %rsi
+; X64: .seh_pushreg 6
 ; X64: subq $32, %rsp
 ; X64: .seh_stackalloc 32
 ; X64: leaq 32(%rdx), %rbp
@@ -131,6 +133,7 @@ catchendblock:                                    ; preds = %catch,
 ; X64: callq f
 ; X64: leaq [[contbb]](%rip), %rax
 ; X64: addq $32, %rsp
+; X64: popq %rsi
 ; X64: popq %rbp
 ; X64: retq
 
-- 
2.34.1