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MachineSink: Sort the successors before trying to find SuccToSinkTo.

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One motivating example is to sink an instruction from a basic block which has
two successors: one outside the loop, the other inside the loop. We should try
to sink the instruction outside the loop.

rdar://11980766


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161062 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manman Ren 2012-07-31 18:10:39 +00:00
parent 8c574be2fe
commit 53b59d1d97
2 changed files with 69 additions and 2 deletions
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17
lib/CodeGen/MachineSink.cpp
View File

@ -99,6 +99,16 @@ namespace {
bool PerformTrivialForwardCoalescing(MachineInstr *MI,
MachineBasicBlock *MBB);
};
// SuccessorSorter - Sort Successors according to their loop depth.
struct SuccessorSorter {
SuccessorSorter(MachineLoopInfo *LoopInfo) : LI(LoopInfo) {}
bool operator()(const MachineBasicBlock *LHS,
const MachineBasicBlock *RHS) const {
return LI->getLoopDepth(LHS) < LI->getLoopDepth(RHS);
}
MachineLoopInfo *LI;
};
} // end anonymous namespace
char MachineSinking::ID = 0;
@ -526,8 +536,11 @@ MachineBasicBlock *MachineSinking::FindSuccToSinkTo(MachineInstr *MI,
// Otherwise, we should look at all the successors and decide which one
// we should sink to.
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
E = MBB->succ_end(); SI != E; ++SI) {
// We give successors with smaller loop depth higher priority.
SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(), MBB->succ_end());
std::sort(Succs.begin(), Succs.end(), SuccessorSorter(LI));
for (SmallVector<MachineBasicBlock*, 4>::iterator SI = Succs.begin(),
E = Succs.end(); SI != E; ++SI) {
MachineBasicBlock *SuccBlock = *SI;
bool LocalUse = false;
if (AllUsesDominatedByBlock(Reg, SuccBlock, MBB,

54
test/CodeGen/X86/sink-out-of-loop.ll Normal file
View File

@ -0,0 +1,54 @@
; RUN: llc -mtriple=x86_64-apple-darwin < %s | FileCheck %s
; A MOV32ri is inside a loop, it has two successors, one successor is inside the
; same loop, the other successor is outside the loop. We should be able to sink
; MOV32ri outside the loop.
; rdar://11980766
define i32 @sink_succ(i32 %argc, i8** nocapture %argv) nounwind uwtable ssp {
; CHECK: sink_succ
; CHECK: [[OUTER_LN1:LBB0_[0-9]+]]: ## %preheader
; CHECK: %exit
; CHECK-NOT: movl
; CHECK: jne [[OUTER_LN1]]
; CHECK: movl
; CHECK: [[LN2:LBB0_[0-9]+]]: ## %for.body2
; CHECK: jne [[LN2]]
; CHECK: ret
entry:
br label %preheader
preheader:
%i.127 = phi i32 [ 0, %entry ], [ %inc9, %exit ]
br label %for.body1.lr
for.body1.lr:
%iv30 = phi i32 [ 1, %preheader ], [ %iv.next31, %for.inc40.i ]
br label %for.body1
for.body1:
%iv.i = phi i64 [ 0, %for.body1.lr ], [ %iv.next.i, %for.body1 ]
%iv.next.i = add i64 %iv.i, 1
%lftr.wideiv32 = trunc i64 %iv.next.i to i32
%exitcond33 = icmp eq i32 %lftr.wideiv32, %iv30
br i1 %exitcond33, label %for.inc40.i, label %for.body1
for.inc40.i:
%iv.next31 = add i32 %iv30, 1
%exitcond49.i = icmp eq i32 %iv.next31, 32
br i1 %exitcond49.i, label %exit, label %for.body1.lr
exit:
%inc9 = add nsw i32 %i.127, 1
%exitcond34 = icmp eq i32 %inc9, 10
br i1 %exitcond34, label %for.body2, label %preheader
for.body2:
%iv = phi i64 [ %iv.next, %for.body2 ], [ 0, %exit ]
%iv.next = add i64 %iv, 1
%lftr.wideiv = trunc i64 %iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, 2048
br i1 %exitcond, label %for.end20, label %for.body2
for.end20:
ret i32 0
}