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[GISel]: Allow PHIs to be DCEd 

https://reviews.llvm.org/D53304

Currently dead phis are not cleaned up during DCE. This patch allows
dead PHI and G_PHI insts to be deleted.

Reviewed by: dsanders

llvm-svn: 344811
This commit is contained in:
Aditya Nandakumar 2018-10-19 20:11:52 +00:00
parent 80ed0fd6e0
commit cd04e366d7
2 changed files with 2 additions and 1 deletions
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2
llvm/lib/CodeGen/GlobalISel/Utils.cpp
View File

@ -137,7 +137,7 @@ bool llvm::isTriviallyDead(const MachineInstr &MI,
// If we can move an instruction, we can remove it. Otherwise, it has
// a side-effect of some sort.
bool SawStore = false;
if (!MI.isSafeToMove(/*AA=*/nullptr, SawStore))
if (!MI.isSafeToMove(/*AA=*/nullptr, SawStore) && !MI.isPHI())
return false;
// Instructions without side-effects are dead iff they only define dead vregs.

1
llvm/test/CodeGen/AArch64/GlobalISel/legalize-phi.mir
View File

@ -121,6 +121,7 @@ body: |
bb.3:
%9(s1) = G_PHI %5(s1), %bb.1, %8(s1), %bb.2
%11:_(s1) = G_PHI %5(s1), %bb.1, %8(s1), %bb.2
%10(s32) = G_ZEXT %9(s1)
$w0 = COPY %10(s32)
RET_ReallyLR implicit $w0