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AArch64: disallow x30 & x29 as the destination for indirect tail calls

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As Ana Pazos pointed out, these have to be restored to their incoming values
before a function returns; i.e. before the tail call. So they can't be used
correctly as the destination register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210525 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover
2014-06-10 10:50:24 +00:00
parent efbf7d1ceb
commit e1db6ac10b
2 changed files with 15 additions and 1 deletions
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14
test/CodeGen/AArch64/regress-tail-livereg.ll
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@@ -17,3 +17,17 @@ define void @foo() {
; CHECK: br {{x([0-79]|1[0-8])}}
ret void
}
; No matter how tempting it is, LLVM should not use x30 since that'll be
; restored to its incoming value before the "br".
define void @test_x30_tail() {
; CHECK-LABEL: test_x30_tail:
; CHECK: mov [[DEST:x[0-9]+]], x30
; CHECK: br [[DEST]]
%addr = call i8* @llvm.returnaddress(i32 0)
%faddr = bitcast i8* %addr to void()*
tail call void %faddr()
ret void
}
declare i8* @llvm.returnaddress(i32)