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.
llvm-svn: 160248
diff --git a/llvm/test/CodeGen/X86/force-align-stack-alloca.ll b/llvm/test/CodeGen/X86/force-align-stack-alloca.ll
index ecef781..6d44559 100644
--- a/llvm/test/CodeGen/X86/force-align-stack-alloca.ll
+++ b/llvm/test/CodeGen/X86/force-align-stack-alloca.ll
@@ -19,10 +19,10 @@
; CHECK: g:
; CHECK: pushl %ebp
; CHECK-NEXT: movl %esp, %ebp
+; CHECK-NEXT: pushl
+; CHECK-NEXT: pushl
; CHECK-NEXT: andl $-32, %esp
-; CHECK-NEXT: pushl
-; CHECK-NEXT: pushl
-; CHECK-NEXT: subl $24, %esp
+; CHECK-NEXT: subl $32, %esp
;
; Now setup the base pointer (%ebx).
; CHECK-NEXT: movl %esp, %ebx
@@ -46,17 +46,13 @@
; 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