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llvm-project/llvm/test/CodeGen/ARM/v8m-tail-call.ll

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[ARM] Change TCReturn to tBL if tailcall optimization fails. Summary: The tail call optimisation is performed before register allocation, so at that point we don't know if LR is being spilt or not. If LR was spilt to the stack, then we cannot do a tail call optimisation. That would involve popping back into LR which is not possible in Thumb1 code. Reviewers: rengolin, jmolloy, rovka, olista01 Reviewed By: olista01 Subscribers: llvm-commits, aemerson Differential Revision: https://reviews.llvm.org/D29020 llvm-svn: 294000
2017-02-03 19:15:53 +08:00
; RUN: llc %s -o - -mtriple=thumbv8m.base | FileCheck %s
[ARM] Fix incorrect conversion of a tail call to an ordinary call When we emit a tail call for Armv8-M, but then discover that the caller needs to save/restore `LR`, we convert the tail call to an ordinary one, since restoring `LR` takes extra instructions, which may negate the benefits of the tail call. If the callee, however, takes stack arguments, this conversion is incorrect, since nothing has been done to pass the stack arguments. Thus the patch reverts https://reviews.llvm.org/rL294000 Also, we improve the instruction sequence for popping `LR` in the case when we couldn't immediately find a scratch low register, but we can use as a temporary one of the callee-saved low registers and restore `LR` before popping other callee-saves. Differential Revision: https://reviews.llvm.org/D39599 llvm-svn: 318143
2017-11-14 18:36:52 +08:00
declare i32 @g(...)
declare i32 @h0(i32, i32, i32, i32)
define hidden i32 @f0() {
%1 = tail call i32 bitcast (i32 (...)* @g to i32 ()*)()
%2 = tail call i32 @h0(i32 %1, i32 1, i32 2, i32 3)
ret i32 %2
; CHECK-LABEL: f0
; CHECK: ldr [[POP:r[4567]]], [sp
; CHECK-NEXT: mov lr, [[POP]]
; CHECK-NEXT: pop {{.*}}[[POP]]
; CHECK-NEXT: add sp, #4
; CHECK-NEXT: b h0
[ARM] Change TCReturn to tBL if tailcall optimization fails. Summary: The tail call optimisation is performed before register allocation, so at that point we don't know if LR is being spilt or not. If LR was spilt to the stack, then we cannot do a tail call optimisation. That would involve popping back into LR which is not possible in Thumb1 code. Reviewers: rengolin, jmolloy, rovka, olista01 Reviewed By: olista01 Subscribers: llvm-commits, aemerson Differential Revision: https://reviews.llvm.org/D29020 llvm-svn: 294000
2017-02-03 19:15:53 +08:00
}
[ARM] Fix incorrect conversion of a tail call to an ordinary call When we emit a tail call for Armv8-M, but then discover that the caller needs to save/restore `LR`, we convert the tail call to an ordinary one, since restoring `LR` takes extra instructions, which may negate the benefits of the tail call. If the callee, however, takes stack arguments, this conversion is incorrect, since nothing has been done to pass the stack arguments. Thus the patch reverts https://reviews.llvm.org/rL294000 Also, we improve the instruction sequence for popping `LR` in the case when we couldn't immediately find a scratch low register, but we can use as a temporary one of the callee-saved low registers and restore `LR` before popping other callee-saves. Differential Revision: https://reviews.llvm.org/D39599 llvm-svn: 318143
2017-11-14 18:36:52 +08:00
declare i32 @h1(i32)
define hidden i32 @f1() {
%1 = tail call i32 bitcast (i32 (...)* @g to i32 ()*)()
%2 = tail call i32 @h1(i32 %1)
ret i32 %2
; CHECK-LABEL: f1
; CHECK: pop {r7}
; CHECK: pop {r1}
; CHECK: mov lr, r1
; CHECK: b h1
[ARM] Change TCReturn to tBL if tailcall optimization fails. Summary: The tail call optimisation is performed before register allocation, so at that point we don't know if LR is being spilt or not. If LR was spilt to the stack, then we cannot do a tail call optimisation. That would involve popping back into LR which is not possible in Thumb1 code. Reviewers: rengolin, jmolloy, rovka, olista01 Reviewed By: olista01 Subscribers: llvm-commits, aemerson Differential Revision: https://reviews.llvm.org/D29020 llvm-svn: 294000
2017-02-03 19:15:53 +08:00
}
[ARM] Fix incorrect conversion of a tail call to an ordinary call When we emit a tail call for Armv8-M, but then discover that the caller needs to save/restore `LR`, we convert the tail call to an ordinary one, since restoring `LR` takes extra instructions, which may negate the benefits of the tail call. If the callee, however, takes stack arguments, this conversion is incorrect, since nothing has been done to pass the stack arguments. Thus the patch reverts https://reviews.llvm.org/rL294000 Also, we improve the instruction sequence for popping `LR` in the case when we couldn't immediately find a scratch low register, but we can use as a temporary one of the callee-saved low registers and restore `LR` before popping other callee-saves. Differential Revision: https://reviews.llvm.org/D39599 llvm-svn: 318143
2017-11-14 18:36:52 +08:00
declare i32 @h2(i32, i32, i32, i32, i32)
define hidden i32 @f2(i32, i32, i32, i32, i32) {
%6 = tail call i32 bitcast (i32 (...)* @g to i32 ()*)()
%7 = icmp eq i32 %6, 0
br i1 %7, label %10, label %8
%9 = tail call i32 @h2(i32 %6, i32 %1, i32 %2, i32 %3, i32 %4)
br label %10
%11 = phi i32 [ %9, %8 ], [ -1, %5 ]
ret i32 %11
; CHECK-LABEL: f2
; CHECK: ldr [[POP:r[4567]]], [sp
; CHECK-NEXT: mov lr, [[POP]]
; CHECK-NEXT: pop {{.*}}[[POP]]
; CHECK-NEXT: add sp, #4
; CHECK-NEXT: b h2
}