[X86] Restore X86 base pointer after call to llvm.eh.sjlj.setjmp

Commit on 

- This patch fixes the bug described in
  http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-May/062343.html

The fix allocates an extra slot just below the GPRs and stores the base pointer
there. This is done only for functions containing llvm.eh.sjlj.setjmp that also
need a base pointer. Because code containing llvm.eh.sjlj.setjmp saves all of
the callee-save GPRs in the prologue, the offset to the extra slot can be
computed before prologue generation runs.

Impact at run-time on affected functions is::

  - One extra store in the prologue, The store saves the base pointer.
  - One extra load after a llvm.eh.sjlj.setjmp. The load restores the base pointer.

Because the extra slot is just above a gap between frame-pointer-relative and
base-pointer-relative chunks of memory, there is no impact on other offset
calculations other than ensuring there is room for the extra slot.

http://reviews.llvm.org/D6388

Patch by Arch Robison <arch.robison@intel.com>



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223329 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86FrameLowering.cpp

@@ -448,6 +448,8 @@ void X86FrameLowering::getStackProbeFunction(const X86Subtarget &STI,
 
   [if needs base pointer]
       mov  %rsp, %rbx
+      [if needs to restore base pointer]
+          mov %rsp, -MMM(%rbp)
 
   ; Emit CFI info
   [if needs FP]
@@ -570,6 +572,9 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const {
   if (HasFP) {
     // Calculate required stack adjustment.
     uint64_t FrameSize = StackSize - SlotSize;
+    // If required, include space for extra hidden slot for stashing base pointer.
+    if (X86FI->getRestoreBasePointer()) 
+      FrameSize += SlotSize;
     if (RegInfo->needsStackRealignment(MF)) {
       // Callee-saved registers are pushed on stack before the stack
       // is realigned.
@@ -838,6 +843,14 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const {
     BuildMI(MBB, MBBI, DL, TII.get(Opc), BasePtr)
       .addReg(StackPtr)
       .setMIFlag(MachineInstr::FrameSetup);
+    if (X86FI->getRestoreBasePointer()) {
+      // Stash value of base pointer.  Saving RSP instead of EBP shortens dependence chain.
+      unsigned Opm = Uses64BitFramePtr ? X86::MOV64mr : X86::MOV32mr;
+      addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opm)),
+                   FramePtr, true, X86FI->getRestoreBasePointerOffset())
+        .addReg(StackPtr)
+        .setMIFlag(MachineInstr::FrameSetup);
+    }
   }
 
   if (((!HasFP && NumBytes) || PushedRegs) && NeedsDwarfCFI) {

lib/Target/X86/X86ISelLowering.cpp

@@ -20925,6 +20925,7 @@ X86TargetLowering::emitEHSjLjSetJmp(MachineInstr *MI,
   //  v = phi(main, restore)
   //
   // restoreMBB:
+  //  if base pointer being used, load it from frame
   //  v_restore = 1
 
   MachineBasicBlock *thisMBB = MBB;
@@ -21008,6 +21009,18 @@ X86TargetLowering::emitEHSjLjSetJmp(MachineInstr *MI,
     .addReg(restoreDstReg).addMBB(restoreMBB);
 
   // restoreMBB:
+  if (RegInfo->hasBasePointer(*MF)) { 
+    const X86Subtarget &STI = MF->getTarget().getSubtarget<X86Subtarget>();
+    const bool Uses64BitFramePtr = STI.isTarget64BitLP64() || STI.isTargetNaCl64();
+    X86MachineFunctionInfo *X86FI = MF->getInfo<X86MachineFunctionInfo>();
+    X86FI->setRestoreBasePointer(MF);
+    unsigned FramePtr = RegInfo->getFrameRegister(*MF);
+    unsigned BasePtr = RegInfo->getBaseRegister();
+    unsigned Opm = Uses64BitFramePtr ? X86::MOV64rm : X86::MOV32rm;
+    addRegOffset(BuildMI(restoreMBB, DL, TII->get(Opm), BasePtr),
+                 FramePtr, true, X86FI->getRestoreBasePointerOffset())
+      .setMIFlag(MachineInstr::FrameSetup);
+  }
   BuildMI(restoreMBB, DL, TII->get(X86::MOV32ri), restoreDstReg).addImm(1);
   BuildMI(restoreMBB, DL, TII->get(X86::JMP_4)).addMBB(sinkMBB);
   restoreMBB->addSuccessor(sinkMBB);

lib/Target/X86/X86MachineFunctionInfo.cpp

@@ -8,7 +8,26 @@
 //===----------------------------------------------------------------------===//
 
 #include "X86MachineFunctionInfo.h"
+#include "X86RegisterInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
 
 using namespace llvm;
 
 void X86MachineFunctionInfo::anchor() { }
+
+void X86MachineFunctionInfo::setRestoreBasePointer(const MachineFunction *MF) {
+  if (!RestoreBasePointerOffset) {
+    const X86RegisterInfo *RegInfo = static_cast<const X86RegisterInfo *>(
+      MF->getSubtarget().getRegisterInfo());
+    unsigned SlotSize = RegInfo->getSlotSize();
+    for (const MCPhysReg *CSR = 
+      RegInfo->X86RegisterInfo::getCalleeSavedRegs(MF);
+      unsigned Reg = *CSR;
+       ++CSR)
+    {
+      if (X86::GR64RegClass.contains(Reg) || X86::GR32RegClass.contains(Reg))
+        RestoreBasePointerOffset -= SlotSize;
+    }
+  }
+}
+

lib/Target/X86/X86MachineFunctionInfo.h

@@ -31,6 +31,12 @@ class X86MachineFunctionInfo : public MachineFunctionInfo {
   /// contains stack pointer re-alignment code which requires FP.
   bool ForceFramePointer;
 
+  /// RestoreBasePointerOffset - Non-zero if the function has base pointer 
+  /// and makes call to llvm.eh.sjlj.setjmp. When non-zero, the value is a 
+  /// displacement from the frame pointer to a slot where the base pointer 
+  /// is stashed. 
+  signed char RestoreBasePointerOffset;
+ 
   /// CalleeSavedFrameSize - Size of the callee-saved register portion of the
   /// stack frame in bytes.
   unsigned CalleeSavedFrameSize;
@@ -89,6 +95,7 @@ private:
 
 public:
   X86MachineFunctionInfo() : ForceFramePointer(false),
+                             RestoreBasePointerOffset(0),
                              CalleeSavedFrameSize(0),
                              BytesToPopOnReturn(0),
                              ReturnAddrIndex(0),
@@ -104,6 +111,7 @@ public:
 
   explicit X86MachineFunctionInfo(MachineFunction &MF)
     : ForceFramePointer(false),
+      RestoreBasePointerOffset(0),
       CalleeSavedFrameSize(0),
       BytesToPopOnReturn(0),
       ReturnAddrIndex(0),
@@ -120,6 +128,10 @@ public:
   bool getForceFramePointer() const { return ForceFramePointer;}
   void setForceFramePointer(bool forceFP) { ForceFramePointer = forceFP; }
 
+  bool getRestoreBasePointer() const { return RestoreBasePointerOffset!=0; }
+  void setRestoreBasePointer(const MachineFunction *MF);
+  int getRestoreBasePointerOffset() const {return RestoreBasePointerOffset; }
+
   unsigned getCalleeSavedFrameSize() const { return CalleeSavedFrameSize; }
   void setCalleeSavedFrameSize(unsigned bytes) { CalleeSavedFrameSize = bytes; }
 

test/CodeGen/X86/sjlj-baseptr.ll

@@ -0,0 +1,37 @@
+; RUN: llc < %s -mtriple=i386-pc-linux -mcpu=corei7 -relocation-model=static | FileCheck --check-prefix=X86 %s
+; RUN: llc < %s -mtriple=x86_64-pc-linux -mcpu=corei7 -relocation-model=static | FileCheck --check-prefix=X64 %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+%Foo = type { [125 x i8] }
+
+declare i32 @llvm.eh.sjlj.setjmp(i8*) nounwind
+
+declare void @whatever(i64, %Foo*, i8**, i8*, i8*, i32)  #0
+
+attributes #0 = { nounwind uwtable "no-frame-pointer-elim"="true" }
+
+define i32 @test1(i64 %n, %Foo* byval nocapture readnone align 8 %f) #0 {
+entry:
+  %buf = alloca [5 x i8*], align 16
+  %p = alloca i8*, align 8
+  %q = alloca i8, align 64
+  %r = bitcast [5 x i8*]* %buf to i8*
+  %s = alloca i8, i64 %n, align 1
+  store i8* %s, i8** %p, align 8
+  %t = call i32 @llvm.eh.sjlj.setjmp(i8* %s)
+  call void @whatever(i64 %n, %Foo* %f, i8** %p, i8* %q, i8* %s, i32 %t) #1
+  ret i32 0
+; X86: movl    %esp, %esi
+; X86: movl    %esp, -16(%ebp)
+; X86: {{.LBB.*:}}
+; X86: movl    -16(%ebp), %esi
+; X86: {{.LBB.*:}}
+; X64: movq    %rsp, %rbx
+; X64: movq    %rsp, -48(%rbp)
+; X64: {{.LBB.*:}}
+; X64: movq    -48(%rbp), %rbx
+; X64: {{.LBB.*:}}
+}
+
+