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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
43 lines
1.2 KiB
LLVM
43 lines
1.2 KiB
LLVM
; RUN: llc < %s -mtriple=thumbv8 -print-machineinstrs=if-converter -arm-atomic-cfg-tidy=0 -o /dev/null 2>&1 | FileCheck %s
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%struct.S = type { i8* (i8*)*, [1 x i8] }
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define internal zeroext i8 @bar(%struct.S* %x, %struct.S* nocapture %y) nounwind readonly {
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entry:
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%0 = getelementptr inbounds %struct.S* %x, i32 0, i32 1, i32 0
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%1 = load i8* %0, align 1
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%2 = zext i8 %1 to i32
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%3 = and i32 %2, 112
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%4 = icmp eq i32 %3, 0
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br i1 %4, label %return, label %bb
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bb:
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%5 = getelementptr inbounds %struct.S* %y, i32 0, i32 1, i32 0
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%6 = load i8* %5, align 1
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%7 = zext i8 %6 to i32
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%8 = and i32 %7, 112
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%9 = icmp eq i32 %8, 0
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br i1 %9, label %return, label %bb2
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; CHECK: BB#2: derived from LLVM BB %bb2
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; CHECK: Successors according to CFG: BB#3(192) BB#4(192)
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bb2:
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%v10 = icmp eq i32 %3, 16
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br i1 %v10, label %bb4, label %bb3, !prof !0
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bb3:
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%v11 = icmp eq i32 %8, 16
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br i1 %v11, label %bb4, label %return, !prof !1
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bb4:
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%v12 = ptrtoint %struct.S* %x to i32
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%phitmp = trunc i32 %v12 to i8
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ret i8 %phitmp
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return:
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ret i8 1
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}
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!0 = metadata !{metadata !"branch_weights", i32 4, i32 12}
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!1 = metadata !{metadata !"branch_weights", i32 8, i32 16}
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