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llvm-mirror/test/Analysis/BasicAA/tail-byval.ll
Reid Kleckner 6e852d9c3d [BasicAA] Don't assume tail calls with byval don't alias allocas
Summary:
Calls marked 'tail' cannot read or write allocas from the current frame
because the current frame might be destroyed by the time they run.
However, a tail call may use an alloca with byval. Calling with byval
copies the contents of the alloca into argument registers or stack
slots, so there is no lifetime issue. Tail calls never modify allocas,
so we can return just ModRefInfo::Ref.

Fixes PR38466, a longstanding bug.

Reviewers: hfinkel, nlewycky, gbiv, george.burgess.iv

Subscribers: hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D50679

llvm-svn: 339636
2018-08-14 01:24:35 +00:00

16 lines
490 B
LLVM

; RUN: opt -basicaa -aa-eval -print-all-alias-modref-info -disable-output < %s 2>&1 | FileCheck %s
declare void @takebyval(i32* byval %p)
define i32 @tailbyval() {
entry:
%p = alloca i32
store i32 42, i32* %p
tail call void @takebyval(i32* byval %p)
%rv = load i32, i32* %p
ret i32 %rv
}
; FIXME: This should be Just Ref.
; CHECK-LABEL: Function: tailbyval: 1 pointers, 1 call sites
; CHECK-NEXT: Both ModRef: Ptr: i32* %p <-> tail call void @takebyval(i32* byval %p)