llvm/test/CodeGen/ARM/tail-call.ll
Oliver Stannard 802d420792 [ARM,AArch64] Do not tail-call to an externally-defined function with weak linkage
Externally-defined functions with weak linkage should not be
tail-called on ARM or AArch64, as the AAELF spec requires normal calls
to undefined weak functions to be replaced with a NOP or jump to the
next instruction. The behaviour of branch instructions in this
situation (as used for tail calls) is implementation-defined, so we
cannot rely on the linker replacing the tail call with a return.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215890 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-18 12:42:15 +00:00

32 lines
830 B
LLVM

; RUN: llc -mtriple armv7 -O0 -o - < %s | FileCheck %s -check-prefix CHECK-TAIL
; RUN: llc -mtriple armv7 -O0 -disable-tail-calls -o - < %s \
; RUN: | FileCheck %s -check-prefix CHECK-NO-TAIL
declare i32 @callee(i32 %i)
declare extern_weak fastcc void @callee_weak()
define i32 @caller(i32 %i) {
entry:
%r = tail call i32 @callee(i32 %i)
ret i32 %r
}
; CHECK-TAIL-LABEL: caller
; CHECK-TAIL: b callee
; CHECK-NO-TAIL-LABEL: caller
; CHECK-NO-TAIL: push {lr}
; CHECK-NO-TAIL: bl callee
; CHECK-NO-TAIL: pop {lr}
; CHECK-NO-TAIL: bx lr
; Weakly-referenced extern functions cannot be tail-called, as AAELF does
; not define the behaviour of branch instructions to undefined weak symbols.
define fastcc void @caller_weak() {
; CHECK-LABEL: caller_weak:
; CHECK: bl callee_weak
tail call void @callee_weak()
ret void
}