This CL changes the function prologue and epilogue emitted on X86 when stack needs realignment.

It is intended to fix PR11468.

Old prologue and epilogue looked like this:
push %rbp
mov %rsp, %rbp
and $alignment, %rsp
push %r14
push %r15
...
pop %r15
pop %r14
mov %rbp, %rsp
pop %rbp

The problem was to reference the locations of callee-saved registers in exception handling:
locations of callee-saved had to be re-calculated regarding the stack alignment operation. It would
take some effort to implement this in LLVM, as currently MachineLocation can only have the form
"Register + Offset". Funciton prologue and epilogue are now changed to:

push %rbp
mov %rsp, %rbp
push %14
push %15
and $alignment, %rsp
...
lea -$size_of_saved_registers(%rbp), %rsp
pop %r15
pop %r14
pop %rbp

Reviewed by Chad Rosier.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160248 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 10 deletions

diff --git a/test/CodeGen/X86/force-align-stack-alloca.ll b/test/CodeGen/X86/force-align-stack-alloca.ll
index ecef781f88..6d44559437 100644
--- a/test/CodeGen/X86/force-align-stack-alloca.ll
+++ b/test/CodeGen/X86/force-align-stack-alloca.ll
@@ -19,10 +19,10 @@ define i64 @g(i32 %i) nounwind {
 ; CHECK: g:
 ; CHECK:      pushl  %ebp
 ; CHECK-NEXT: movl   %esp, %ebp
-; CHECK-NEXT: andl   $-32, %esp
 ; CHECK-NEXT: pushl
 ; CHECK-NEXT: pushl
-; CHECK-NEXT: subl   $24, %esp
+; CHECK-NEXT: andl   $-32, %esp
+; CHECK-NEXT: subl   $32, %esp
 ;
 ; Now setup the base pointer (%ebx).
 ; CHECK-NEXT: movl   %esp, %ebx
@@ -46,17 +46,13 @@ define i64 @g(i32 %i) nounwind {
 ; CHECK-NEXT: addl   $32, %esp
 ; CHECK-NOT:         {{[^ ,]*}}, %esp
 ;
-; Restore %esp from %ebx (base pointer) so we can pop the callee-saved
-; registers.  This is the state prior to the allocation of VLAs.
+; Restore %esp from %ebp (frame pointer) and subtract the size of
+; zone with callee-saved registers to pop them.
+; This is the state prior to stack realignment and the allocation of VLAs.
 ; CHECK-NOT:  popl
-; CHECK:      movl   %ebx, %esp
-; CHECK-NEXT: addl   $24, %esp
+; CHECK:      leal   -8(%ebp), %esp
 ; CHECK-NEXT: popl
 ; CHECK-NEXT: popl
-;
-; Finally we need to restore %esp from %ebp due to dynamic stack
-; realignment.
-; CHECK-NEXT: movl   %ebp, %esp
 ; CHECK-NEXT: popl   %ebp
 ; CHECK-NEXT: ret