[llvm] r253245 - [WinEH] Don't let UnwindHelp alias the return address

[Reid Kleckner via llvm-commits]

Author: rnk
Date: Mon Nov 16 12:47:25 2015
New Revision: 253245

URL: http://llvm.org/viewvc/llvm-project?rev=253245&view=rev
Log:
[WinEH] Don't let UnwindHelp alias the return address

On top of that, don't bother allocating and initializing UnwindHelp if
we don't have any funclets. Currently we always use RBP as our frame
pointer when funclets are present, so this change makes it impossible to
come here without any fixed stack objects.

Fixes PR25533.

Added:
    llvm/trunk/test/CodeGen/X86/wineh-no-ehpads.ll
Modified:
    llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
    llvm/trunk/test/CodeGen/X86/win-cleanuppad.ll

Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=253245&r1=253244&r2=253245&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Mon Nov 16 12:47:25 2015
@@ -2662,17 +2662,17 @@ void X86FrameLowering::processFunctionBe
   // If this function isn't doing Win64-style C++ EH, we don't need to do
   // anything.
   const Function *Fn = MF.getFunction();
-  if (!STI.is64Bit() || !Fn->hasPersonalityFn() ||
-      classifyEHPersonality(MF.getFunction()->getPersonalityFn()) !=
-          EHPersonality::MSVC_CXX)
+  if (!STI.is64Bit() || !MF.getMMI().hasEHFunclets() ||
+      classifyEHPersonality(Fn->getPersonalityFn()) != EHPersonality::MSVC_CXX)
     return;
 
   // Win64 C++ EH needs to allocate the UnwindHelp object at some fixed offset
   // relative to RSP after the prologue.  Find the offset of the last fixed
-  // object, so that we can allocate a slot immediately following it. Fixed
-  // objects have negative frame indices.
+  // object, so that we can allocate a slot immediately following it. If there
+  // were no fixed objects, use offset -SlotSize, which is immediately after the
+  // return address. Fixed objects have negative frame indices.
   MachineFrameInfo *MFI = MF.getFrameInfo();
-  int64_t MinFixedObjOffset = 0;
+  int64_t MinFixedObjOffset = -SlotSize;
   for (int I = MFI->getObjectIndexBegin(); I < 0; ++I)
     MinFixedObjOffset = std::min(MinFixedObjOffset, MFI->getObjectOffset(I));
 

Modified: llvm/trunk/test/CodeGen/X86/win-cleanuppad.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/win-cleanuppad.ll?rev=253245&r1=253244&r2=253245&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/win-cleanuppad.ll (original)
+++ llvm/trunk/test/CodeGen/X86/win-cleanuppad.ll Mon Nov 16 12:47:25 2015
@@ -19,6 +19,36 @@ ehcleanup:
   cleanupret %0 unwind to caller
 }
 
+; CHECK: simple_cleanup:                         # @simple_cleanup
+; CHECK:         pushq   %rbp
+; CHECK:         subq    $48, %rsp
+; CHECK:         leaq    48(%rsp), %rbp
+; CHECK:         movq    $-2, -8(%rbp)
+; CHECK:         movl    $1, %ecx
+; CHECK:         callq   f
+; CHECK:         callq   "??1Dtor@@QAE at XZ"
+; CHECK:         nop
+; CHECK:         addq    $48, %rsp
+; CHECK:         popq    %rbp
+; CHECK:         retq
+
+; CHECK: "?dtor$2@?0?simple_cleanup at 4HA":
+; CHECK:         callq   "??1Dtor@@QAE at XZ"
+; CHECK:         retq
+
+; CHECK: $cppxdata$simple_cleanup:
+; CHECK-NEXT:         .long   429065506
+; CHECK-NEXT:         .long   1
+; CHECK-NEXT:         .long   ($stateUnwindMap$simple_cleanup)@IMGREL
+; CHECK-NEXT:         .long   0
+; CHECK-NEXT:         .long   0
+; CHECK-NEXT:         .long   3
+; CHECK-NEXT:         .long   ($ip2state$simple_cleanup)@IMGREL
+; UnwindHelp offset should match the -2 store above
+; CHECK-NEXT:         .long   40
+; CHECK-NEXT:         .long   0
+; CHECK-NEXT:         .long   1
+
 declare void @f(i32) #0
 
 declare i32 @__CxxFrameHandler3(...)

Added: llvm/trunk/test/CodeGen/X86/wineh-no-ehpads.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/wineh-no-ehpads.ll?rev=253245&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/wineh-no-ehpads.ll (added)
+++ llvm/trunk/test/CodeGen/X86/wineh-no-ehpads.ll Mon Nov 16 12:47:25 2015
@@ -0,0 +1,20 @@
+; RUN: llc < %s | FileCheck %s
+
+target triple = "x86_64-pc-windows-msvc"
+
+declare void @g()
+declare i32 @__CxxFrameHandler3(...)
+
+define void @personality_no_ehpad() personality i32 (...)* @__CxxFrameHandler3 {
+  call void @g()
+  ret void
+}
+
+; CHECK-LABEL: personality_no_ehpad: # @personality_no_ehpad
+; CHECK-NOT: movq $-2,
+; CHECK: callq g
+; CHECK: nop
+; CHECK: retq
+
+; Shouldn't have any LSDA either.
+; CHECK-NOT: cppxdata