mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-21 00:32:23 +00:00
d0dbe02fd2
The C and C++ semantics for compare_exchange require it to return a bool
indicating success. This gets mapped to LLVM IR which follows each cmpxchg with
an icmp of the value loaded against the desired value.
When lowered to ldxr/stxr loops, this extra comparison is redundant: its
results are implicit in the control-flow of the function.
This commit makes two changes: it replaces that icmp with appropriate PHI
nodes, and then makes sure earlyCSE is called after expansion to actually make
use of the opportunities revealed.
I've also added -{arm,aarch64}-enable-atomic-tidy options, so that
existing fragile tests aren't perturbed too much by the change. Many
of them either rely on undef/unreachable too pervasively to be
restored to something well-defined (particularly while making sure
they test the same obscure assert from many years ago), or depend on a
particular CFG shape, which is disrupted by SimplifyCFG.
rdar://problem/16227836
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209883 91177308-0d34-0410-b5e6-96231b3b80d8
36 lines
930 B
LLVM
36 lines
930 B
LLVM
; RUN: llc -mtriple=aarch64-none-linux-gnu -aarch64-atomic-cfg-tidy=0 -verify-machineinstrs -o - %s | FileCheck %s
|
|
|
|
; LLVM should be able to cope with multiple uses of the same flag-setting
|
|
; instruction at different points of a routine. Either by rematerializing the
|
|
; compare or by saving and restoring the flag register.
|
|
|
|
declare void @bar()
|
|
|
|
@var = global i32 0
|
|
|
|
define i32 @test_multiflag(i32 %n, i32 %m, i32 %o) {
|
|
; CHECK-LABEL: test_multiflag:
|
|
|
|
%test = icmp ne i32 %n, %m
|
|
; CHECK: cmp [[LHS:w[0-9]+]], [[RHS:w[0-9]+]]
|
|
|
|
%val = zext i1 %test to i32
|
|
; CHECK: cset {{[xw][0-9]+}}, ne
|
|
|
|
store i32 %val, i32* @var
|
|
|
|
call void @bar()
|
|
; CHECK: bl bar
|
|
|
|
; Currently, the comparison is emitted again. An MSR/MRS pair would also be
|
|
; acceptable, but assuming the call preserves NZCV is not.
|
|
br i1 %test, label %iftrue, label %iffalse
|
|
; CHECK: cmp [[LHS]], [[RHS]]
|
|
; CHECK: b.eq
|
|
|
|
iftrue:
|
|
ret i32 42
|
|
iffalse:
|
|
ret i32 0
|
|
}
|