[X86][x32] Save callee-save register used as base pointer for x32 ABI

[pbhatu]

Summary

For the x32 ABI, since the base pointer register (EBX) is a callee save register
it should be saved before use.

This fixes https://bugs.llvm.org/show_bug.cgi?id=36011

[pbhatu]

Ping!

[dschuff]

Sorry this slipped through; this looks right to me.

[pbhatu]

Can you please commit it for me? I don't have commit access.

[dschuff]

test/CodeGen/X86/x86-64-baseptr.ll

56

Actually the epilog needs to be updated in the test too. It's now

leal	-8(%ebp), %esp
	popq	%rbx
	popq	%rbp

lib/Target/X86/X86FrameLowering.cpp

 }
 
 void X86FrameLowering::determineCalleeSaves(MachineFunction &MF,
                                             BitVector &SavedRegs,
                                             RegScavenger *RS) const {
   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
 
   // Spill the BasePtr if it's used.
-  if (TRI->hasBasePointer(MF))
-    SavedRegs.set(TRI->getBaseRegister());
+  if (TRI->hasBasePointer(MF)){
+    unsigned BasePtr = TRI->getBaseRegister();
+    if (STI.isTarget64BitILP32())
+      BasePtr = getX86SubSuperRegister(BasePtr, 64);
+    SavedRegs.set(BasePtr);
+  }
 }
 
 static bool
 HasNestArgument(const MachineFunction *MF) {
   const Function &F = MF->getFunction();
   for (Function::const_arg_iterator I = F.arg_begin(), E = F.arg_end();
        I != E; I++) {
     if (I->hasNestAttr())

test/CodeGen/X86/x86-64-baseptr.ll

 ; CHECK-NEXT:    popq %rbx
 ; CHECK-NEXT:    popq %rbp
 ; CHECK-NEXT:    retq
 ;
 ; X32ABI-LABEL: base:
 ; X32ABI:       # %bb.0: # %entry
 ; X32ABI-NEXT:    pushq %rbp
 ; X32ABI-NEXT:    movl %esp, %ebp
+; X32ABI-NEXT:    pushq  %rbx
 ; X32ABI-NEXT:    andl $-32, %esp
 ; X32ABI-NEXT:    subl $32, %esp
 ; X32ABI-NEXT:    movl %esp, %ebx
 ; X32ABI-NEXT:    callq helper
 ; X32ABI-NEXT:    # kill: def %eax killed %eax def %rax
 ; X32ABI-NEXT:    movl %esp, %ecx
 ; X32ABI-NEXT:    leal 31(,%rax,4), %eax
 ; X32ABI-NEXT:    andl $-32, %eax
 ; X32ABI-NEXT:    movl %ecx, %edx
 ; X32ABI-NEXT:    subl %eax, %edx
 ; X32ABI-NEXT:    movl %edx, %esp
 ; X32ABI-NEXT:    negl %eax
 ; X32ABI-NEXT:    movl $0, (%ecx,%eax)
 ; X32ABI-NEXT:    movl %ebp, %esp
 ; X32ABI-NEXT:    popq %rbp
 ; X32ABI-NEXT:    retq
 entry:
   %k = call i32 @helper()
   %a = alloca i32, i32 %k, align 4
   store i32 0, i32* %a, align 4
   ret void
 }
 
 attributes #0 = { nounwind "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"}