f82023d72e
The commit in [1] changes the behavior of the Arm backend for the attribute frame-pointer=all. Before [1], leaf functions marked with frame-pointer=all were not emitting the frame-pointer. After [1], frame-pointer=all started generating frame pointer for all functions, including leaf functions. However, the default behavior for the driver in clang is to emit the command line option `-mframe-pointer=all` on Arm, if no options for handling the frame pointer is specified at command line. This causes observable regressions. This patch addresses these regressions by configuring the driver so to emit `-mframe-pointer=non-leaf` when targeting Arm. Codegen tests dealing with frame pointer generation have been extended to handle functions with a tail call, since this configuration was missing. [1] 4a2bd78f5b0d0661c23dff9c4b93a393a49dbf9a
161 lines
4.4 KiB
LLVM
161 lines
4.4 KiB
LLVM
; 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() "frame-pointer"="none" {
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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() "frame-pointer"="all" {
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; CHECK-LABEL: leaf_lowreg_nofpelim:
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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}
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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() "frame-pointer"="all" {
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; CHECK-LABEL: leaf_highreg_nofpelim:
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; CHECK: push {r6, 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: ldr r8, [sp], #4
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; CHECK: pop {r6, r7, pc}
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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() "frame-pointer"="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() "frame-pointer"="all" {
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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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; Has a call, and frame pointer requested for non-leaf function.
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define void @call_nononleaffpelim() "frame-pointer"="non-leaf" {
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; CHECK-LABEL: call_nononleaffpelim:
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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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define void @call_nononleaffpelim_tailcall() "frame-pointer"="non-leaf" {
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; CHECK-LABEL: call_nononleaffpelim_tailcall:
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; CHECK-NOT: push
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; CHECK: b foo
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tail call void @foo()
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ret void
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}
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; Has a high register clobbered, no need for a frame pointer.
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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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}
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; Has a high register clobbered, frame pointer requested. We need to split the
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; push into two, to ensure that r7 and sp are adjacent on the stack.
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define void @highreg_nofpelim() "frame-pointer"="all" {
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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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}
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; Has a high register clobbered, frame required due to variable-sized alloca.
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; We need a frame pointer to correctly restore the stack, but don't need to
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; 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
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}
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; Has a high register clobbered, frame required due to both variable-sized
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; alloca and ABI. We do need to split the push/pop here.
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define void @highreg_alloca_nofpelim(i32 %a) "frame-pointer"="all" {
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; CHECK-LABEL: highreg_alloca_nofpelim:
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; CHECK: push {[[SOMEREGS:.*]], r7, lr}
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; CHECK: add r7, sp, #{{[0-9]+}}
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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 {[[SOMEREGS]], r7, 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
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}
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