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3bb84c9bcc
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
llvm-svn: 209883
32 lines
1.1 KiB
LLVM
32 lines
1.1 KiB
LLVM
; RUN: llc %s -o - -aarch64-atomic-cfg-tidy=0 | FileCheck %s
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; Check that ANDS (tst) is not merged with ADD when the immediate
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; is not 0.
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; <rdar://problem/16693089>
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target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
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target triple = "arm64-apple-ios"
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; CHECK-LABEL: tst1:
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; CHECK: add [[REG:w[0-9]+]], w{{[0-9]+}}, #1
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; CHECK: tst [[REG]], #0x1
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define void @tst1(i1 %tst, i32 %true) {
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entry:
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br i1 %tst, label %for.end, label %for.body
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for.body: ; preds = %for.body, %entry
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%result.09 = phi i32 [ %add2.result.0, %for.body ], [ 1, %entry ]
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%i.08 = phi i32 [ %inc, %for.body ], [ 2, %entry ]
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%and = and i32 %i.08, 1
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%cmp1 = icmp eq i32 %and, 0
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%add2.result.0 = select i1 %cmp1, i32 %true, i32 %result.09
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%inc = add nsw i32 %i.08, 1
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%cmp = icmp slt i32 %i.08, %true
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br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge
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for.cond.for.end_crit_edge: ; preds = %for.body
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%add2.result.0.lcssa = phi i32 [ %add2.result.0, %for.body ]
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br label %for.end
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for.end: ; preds = %for.cond.for.end_crit_edge, %entry
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ret void
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}
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