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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
44 lines
1.4 KiB
LLVM
44 lines
1.4 KiB
LLVM
; RUN: llc < %s -mtriple=arm-apple-ios -arm-atomic-cfg-tidy=0 -mcpu=cortex-a9 | FileCheck %s
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; rdar://8402126
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; Make sure if-converter is not predicating vldmia and ldmia. These are
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; micro-coded and would have long issue latency even if predicated on
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; false predicate.
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define void @t(double %a, double %b, double %c, double %d, i32* nocapture %solutions, double* nocapture %x) nounwind {
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entry:
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; CHECK-LABEL: t:
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; CHECK: vpop {d8}
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; CHECK-NOT: vpopne
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; CHECK: pop {r7, pc}
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; CHECK: vpop {d8}
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; CHECK: pop {r7, pc}
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br i1 undef, label %if.else, label %if.then
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if.then: ; preds = %entry
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%mul73 = fmul double undef, 0.000000e+00
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%sub76 = fsub double %mul73, undef
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store double %sub76, double* undef, align 4
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%call88 = tail call double @cos(double 0.000000e+00) nounwind
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%mul89 = fmul double undef, %call88
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%sub92 = fsub double %mul89, undef
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store double %sub92, double* undef, align 4
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ret void
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if.else: ; preds = %entry
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%tmp101 = tail call double @llvm.pow.f64(double undef, double 0x3FD5555555555555)
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%add112 = fadd double %tmp101, undef
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%mul118 = fmul double %add112, undef
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store double 0.000000e+00, double* %x, align 4
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ret void
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}
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declare double @acos(double)
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declare double @sqrt(double) readnone
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declare double @cos(double) readnone
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declare double @fabs(double)
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declare double @llvm.pow.f64(double, double) nounwind readonly
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