[ARM] Generate consistent frame records for Thumb2
There is not an official documented ABI for frame pointers in Thumb2,
but we should try to emit something which is useful.
We use r7 as the frame pointer for Thumb code, which currently means
that if a function needs to save a high register (r8-r11), it will get
pushed to the stack between the frame pointer (r7) and link register
(r14). This means that while a stack unwinder can follow the chain of
frame pointers up the stack, it cannot know the offset to lr, so does
not know which functions correspond to the stack frames.
To fix this, we need to push the callee-saved registers in two batches,
with the first push saving the low registers, fp and lr, and the second
push saving the high registers. This is already implemented, but
previously only used for iOS. This patch turns it on for all Thumb2
targets when frame pointers are required by the ABI, and the frame
pointer is r7 (Windows uses r11, so this isn't a problem there). If
frame pointer elimination is enabled we still emit a single push/pop
even if we need a frame pointer for other reasons, to avoid increasing
code size.
We must also ensure that lr is pushed to the stack when using a frame
pointer, so that we end up with a complete frame record. Situations that
could cause this were rare, because we already push lr in most
situations so that we can return using the pop instruction.
Differential Revision: https://reviews.llvm.org/D23516
llvm-svn: 279506
2016-08-23 17:19:22 +08:00
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; RUN: llc -mtriple=thumbv7m-none-eabi -o - %s | FileCheck %s
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declare void @foo()
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; Leaf function, no frame so no need for a frame pointer.
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define void @leaf() {
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; CHECK-LABEL: leaf:
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; CHECK-NOT: push
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; CHECK-NOT: sp
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; CHECK-NOT: pop
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; CHECK: bx lr
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ret void
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}
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; Leaf function, frame pointer is requested but we don't need any stack frame,
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; so don't create a frame pointer.
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define void @leaf_nofpelim() "no-frame-pointer-elim"="true" {
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; CHECK-LABEL: leaf_nofpelim:
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; CHECK-NOT: push
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; CHECK-NOT: sp
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; CHECK-NOT: pop
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; CHECK: bx lr
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ret void
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}
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; Leaf function, frame pointer is requested and we need a stack frame, so we
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; need to use a frame pointer.
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define void @leaf_lowreg_nofpelim() "no-frame-pointer-elim"="true" {
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; CHECK-LABEL: leaf_lowreg_nofpelim:
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2016-10-12 05:14:03 +08:00
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; CHECK: push {r4, r6, r7, lr}
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; CHECK: add r7, sp, #8
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; CHECK: pop {r4, r6, r7, pc}
|
[ARM] Generate consistent frame records for Thumb2
There is not an official documented ABI for frame pointers in Thumb2,
but we should try to emit something which is useful.
We use r7 as the frame pointer for Thumb code, which currently means
that if a function needs to save a high register (r8-r11), it will get
pushed to the stack between the frame pointer (r7) and link register
(r14). This means that while a stack unwinder can follow the chain of
frame pointers up the stack, it cannot know the offset to lr, so does
not know which functions correspond to the stack frames.
To fix this, we need to push the callee-saved registers in two batches,
with the first push saving the low registers, fp and lr, and the second
push saving the high registers. This is already implemented, but
previously only used for iOS. This patch turns it on for all Thumb2
targets when frame pointers are required by the ABI, and the frame
pointer is r7 (Windows uses r11, so this isn't a problem there). If
frame pointer elimination is enabled we still emit a single push/pop
even if we need a frame pointer for other reasons, to avoid increasing
code size.
We must also ensure that lr is pushed to the stack when using a frame
pointer, so that we end up with a complete frame record. Situations that
could cause this were rare, because we already push lr in most
situations so that we can return using the pop instruction.
Differential Revision: https://reviews.llvm.org/D23516
llvm-svn: 279506
2016-08-23 17:19:22 +08:00
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call void asm sideeffect "", "~{r4}" ()
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ret void
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}
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; Leaf function, frame pointer is requested and we need a stack frame, so we
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; need to use a frame pointer. A high register is pushed to the stack, so we
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; must use two push/pop instructions to ensure that fp and sp are adjacent on
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; the stack.
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define void @leaf_highreg_nofpelim() "no-frame-pointer-elim"="true" {
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; CHECK-LABEL: leaf_highreg_nofpelim:
|
2016-10-12 05:14:03 +08:00
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; CHECK: push {r6, r7, lr}
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; CHECK: add r7, sp, #4
|
[ARM] Generate consistent frame records for Thumb2
There is not an official documented ABI for frame pointers in Thumb2,
but we should try to emit something which is useful.
We use r7 as the frame pointer for Thumb code, which currently means
that if a function needs to save a high register (r8-r11), it will get
pushed to the stack between the frame pointer (r7) and link register
(r14). This means that while a stack unwinder can follow the chain of
frame pointers up the stack, it cannot know the offset to lr, so does
not know which functions correspond to the stack frames.
To fix this, we need to push the callee-saved registers in two batches,
with the first push saving the low registers, fp and lr, and the second
push saving the high registers. This is already implemented, but
previously only used for iOS. This patch turns it on for all Thumb2
targets when frame pointers are required by the ABI, and the frame
pointer is r7 (Windows uses r11, so this isn't a problem there). If
frame pointer elimination is enabled we still emit a single push/pop
even if we need a frame pointer for other reasons, to avoid increasing
code size.
We must also ensure that lr is pushed to the stack when using a frame
pointer, so that we end up with a complete frame record. Situations that
could cause this were rare, because we already push lr in most
situations so that we can return using the pop instruction.
Differential Revision: https://reviews.llvm.org/D23516
llvm-svn: 279506
2016-08-23 17:19:22 +08:00
|
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; CHECK: str r8, [sp, #-4]!
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; CHECK: ldr r8, [sp], #4
|
2016-10-12 05:14:03 +08:00
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|
; CHECK: pop {r6, r7, pc}
|
[ARM] Generate consistent frame records for Thumb2
There is not an official documented ABI for frame pointers in Thumb2,
but we should try to emit something which is useful.
We use r7 as the frame pointer for Thumb code, which currently means
that if a function needs to save a high register (r8-r11), it will get
pushed to the stack between the frame pointer (r7) and link register
(r14). This means that while a stack unwinder can follow the chain of
frame pointers up the stack, it cannot know the offset to lr, so does
not know which functions correspond to the stack frames.
To fix this, we need to push the callee-saved registers in two batches,
with the first push saving the low registers, fp and lr, and the second
push saving the high registers. This is already implemented, but
previously only used for iOS. This patch turns it on for all Thumb2
targets when frame pointers are required by the ABI, and the frame
pointer is r7 (Windows uses r11, so this isn't a problem there). If
frame pointer elimination is enabled we still emit a single push/pop
even if we need a frame pointer for other reasons, to avoid increasing
code size.
We must also ensure that lr is pushed to the stack when using a frame
pointer, so that we end up with a complete frame record. Situations that
could cause this were rare, because we already push lr in most
situations so that we can return using the pop instruction.
Differential Revision: https://reviews.llvm.org/D23516
llvm-svn: 279506
2016-08-23 17:19:22 +08:00
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|
call void asm sideeffect "", "~{r8}" ()
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|
|
ret void
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}
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; Leaf function, frame pointer requested for non-leaf functions only, so no
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; need for a stack frame.
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define void @leaf_nononleaffpelim() "no-frame-pointer-elim-non-leaf" {
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; CHECK-LABEL: leaf_nononleaffpelim:
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; CHECK-NOT: push
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; CHECK-NOT: sp
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; CHECK-NOT: pop
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; CHECK: bx lr
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ret void
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}
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; Has a call, but still no need for a frame pointer.
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define void @call() {
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; CHECK-LABEL: call:
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; CHECK: push {[[DUMMYREG:r[0-9]+]], lr}
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; CHECK-NOT: sp
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; CHECK: bl foo
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; CHECK: pop {[[DUMMYREG]], pc}
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call void @foo()
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ret void
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}
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; Has a call, and frame pointer requested.
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define void @call_nofpelim() "no-frame-pointer-elim"="true" {
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; CHECK-LABEL: call_nofpelim:
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; CHECK: push {r7, lr}
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; CHECK: mov r7, sp
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; CHECK: bl foo
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; CHECK: pop {r7, pc}
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call void @foo()
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ret void
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}
|
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|
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; Has a call, and frame pointer requested for non-leaf function.
|
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|
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define void @call_nononleaffpelim() "no-frame-pointer-elim-non-leaf" {
|
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|
|
; CHECK-LABEL: call_nononleaffpelim:
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|
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; CHECK: push {r7, lr}
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; CHECK: mov r7, sp
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|
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; CHECK: bl foo
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|
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; CHECK: pop {r7, pc}
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|
|
call void @foo()
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ret void
|
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|
|
}
|
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|
|
|
|
|
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|
|
; Has a high register clobbered, no need for a frame pointer.
|
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|
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define void @highreg() {
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; CHECK-LABEL: highreg:
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|
|
; CHECK: push.w {r8, lr}
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; CHECK-NOT: sp
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|
|
; CHECK: bl foo
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|
|
; CHECK: pop.w {r8, pc}
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|
|
call void asm sideeffect "", "~{r8}" ()
|
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|
|
call void @foo()
|
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|
ret void
|
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|
|
}
|
|
|
|
|
|
|
|
|
|
; Has a high register clobbered, frame pointer requested. We need to split the
|
|
|
|
|
; push into two, to ensure that r7 and sp are adjacent on the stack.
|
|
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|
|
define void @highreg_nofpelim() "no-frame-pointer-elim"="true" {
|
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|
|
; CHECK-LABEL: highreg_nofpelim:
|
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|
|
; CHECK: push {[[DUMMYREG:r[0-9]+]], r7, lr}
|
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|
|
; CHECK: add r7, sp, #4
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|
|
; CHECK: str r8, [sp, #-4]!
|
|
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|
|
; CHECK: bl foo
|
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|
|
; CHECK: ldr r8, [sp], #4
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|
|
; CHECK: pop {[[DUMMYREG]], r7, pc}
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|
|
call void asm sideeffect "", "~{r8}" ()
|
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|
|
call void @foo()
|
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|
|
ret void
|
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|
|
}
|
|
|
|
|
|
|
|
|
|
; Has a high register clobbered, frame required due to variable-sized alloca.
|
|
|
|
|
; We need a frame pointer to correctly restore the stack, but don't need to
|
|
|
|
|
; split the push/pop here, because the frame pointer not required by the ABI.
|
|
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|
|
define void @highreg_alloca(i32 %a) {
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|
|
; CHECK-LABEL: highreg_alloca:
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|
; CHECK: push.w {[[SOMEREGS:.*]], r7, r8, lr}
|
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|
|
; CHECK: add r7, sp, #{{[0-9]+}}
|
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|
|
; CHECK: bl foo
|
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|
|
; CHECK: pop.w {[[SOMEREGS]], r7, r8, pc}
|
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|
|
%alloca = alloca i32, i32 %a, align 4
|
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|
|
call void @foo()
|
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|
|
call void asm sideeffect "", "~{r8}" ()
|
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|
|
|
ret void
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; Has a high register clobbered, frame required due to both variable-sized
|
|
|
|
|
; alloca and ABI. We do need to split the push/pop here.
|
|
|
|
|
define void @highreg_alloca_nofpelim(i32 %a) "no-frame-pointer-elim"="true" {
|
|
|
|
|
; CHECK-LABEL: highreg_alloca_nofpelim:
|
|
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|
|
; CHECK: push {[[SOMEREGS:.*]], r7, lr}
|
|
|
|
|
; CHECK: add r7, sp, #{{[0-9]+}}
|
|
|
|
|
; CHECK: str r8, [sp, #-4]!
|
|
|
|
|
; CHECK: bl foo
|
|
|
|
|
; CHECK: ldr r8, [sp], #4
|
|
|
|
|
; CHECK: pop {[[SOMEREGS]], r7, pc}
|
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|
|
%alloca = alloca i32, i32 %a, align 4
|
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|
|
|
call void @foo()
|
|
|
|
|
call void asm sideeffect "", "~{r8}" ()
|
|
|
|
|
ret void
|
|
|
|
|
}
|