llvm-6502/arm64-frame-index.ll at d40b451727ce9d8dc753bb2fb39709b10a541cd2 - llvm-6502 - Applefritter: Git

6502/llvm-6502

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Tim Northover d0dbe02fd2 ARM & AArch64: make use of common cmpxchg idioms after expansion

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

2014-05-30 10:09:59 +00:00

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 ; RUN: llc -march=arm64 -mtriple=arm64-apple-ios -aarch64-atomic-cfg-tidy=0 < %s | FileCheck %s
 ; rdar://11935841
 define void @t1() nounwind ssp {
 entry:
 ; CHECK-LABEL: t1:
 ; CHECK-NOT: add x{{[0-9]+}}, sp
 ; CHECK: stp x28, x27, [sp, #-16]!
   %v = alloca [288 x i32], align 4
   unreachable
 }