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LiveVariables add implicit kills to correctly track partial register kills. This works well enough and is fairly accurate. But coalescer can make it impossible to maintain these markers. e.g.
BL <ga:sss1>, %R0<kill,undef>, %S0<kill>, %R0<imp-def>, %R1<imp-def,dead>, %R2<imp-def,dead>, %R3<imp-def,dead>, %R12<imp-def,dead>, %LR<imp-def,dead>, %D0<imp-def>, ...
...
%reg1031<def> = FLDS <cp#1>, 0, 14, %reg0, Mem:LD4[ConstantPool]
...
%S0<def> = FCPYS %reg1031<kill>, 14, %reg0, %D0<imp-use,kill>
When reg1031 and S0 are coalesced, the copy (FCPYS) will be eliminated the the implicit-kill of D0 is lost. In this case it's possible to move the marker to the FLDS. But in many cases, this is not possible. Suppose
%reg1031<def> = FOO <cp#1>, %D0<imp-def>
...
%S0<def> = FCPYS %reg1031<kill>, 14, %reg0, %D0<imp-use,kill>
When FCPYS goes away, the definition of S0 is the "FOO" instruction. However, transferring the D0 implicit-kill to FOO doesn't work since it is the def of D0 itself. We need to fix this in another time by introducing a "kill" pseudo instruction to track liveness.
Disabling the assertion is not ideal, but machine verifier is doing that job now. It's important to know double-def is not a miscomputation since it means a register should be free but it's not tracked as free. It's a performance issue instead.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82677 91177308-0d34-0410-b5e6-96231b3b80d8
22 lines
948 B
LLVM
22 lines
948 B
LLVM
; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mattr=+neon
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; PR5024
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%struct.1 = type { %struct.4, %struct.4 }
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%struct.4 = type { <4 x float> }
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define arm_aapcs_vfpcc %struct.1* @hhh3(%struct.1* %this, <4 x float> %lenation.0, <4 x float> %legalation.0) nounwind {
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entry:
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%0 = call arm_aapcs_vfpcc %struct.4* @sss1(%struct.4* undef, float 0.000000e+00) nounwind ; <%struct.4*> [#uses=0]
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%1 = call arm_aapcs_vfpcc %struct.4* @qqq1(%struct.4* null, float 5.000000e-01) nounwind ; <%struct.4*> [#uses=0]
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%val92 = load <4 x float>* null ; <<4 x float>> [#uses=1]
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%2 = call arm_aapcs_vfpcc %struct.4* @zzz2(%struct.4* undef, <4 x float> %val92) nounwind ; <%struct.4*> [#uses=0]
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ret %struct.1* %this
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}
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declare arm_aapcs_vfpcc %struct.4* @qqq1(%struct.4*, float) nounwind
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declare arm_aapcs_vfpcc %struct.4* @sss1(%struct.4*, float) nounwind
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declare arm_aapcs_vfpcc %struct.4* @zzz2(%struct.4*, <4 x float>) nounwind
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