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[ModuloSchedule] Fix epilogue peeling with illegal phi.

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When peeling out the epilogue we need to ignore illegal phis coming from stages
greater than the producer stage. Otherwise we end up with circular phi
dependencies.

Differential Revision: https://reviews.llvm.org/D79581
This commit is contained in:
Thomas Raoux 2020-05-07 08:30:00 -07:00
parent 5ac1d35e81
commit 4bd56a4510
3 changed files with 72 additions and 5 deletions
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6
include/llvm/CodeGen/ModuloSchedule.h
View File

@ -141,6 +141,12 @@ public:
return I == Cycle.end() ? -1 : I->second;
}
/// Set the stage of a newly created instruction.
void setStage(MachineInstr *MI, int MIStage) {
assert(Stage.count(MI) == 0);
Stage[MI] = MIStage;
}
/// Return the rescheduled instructions in order.
ArrayRef<MachineInstr *> getInstructions() { return ScheduledInstrs; }

14
lib/CodeGen/ModuloSchedule.cpp
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@ -1440,11 +1440,15 @@ Register KernelRewriter::remapUse(Register Reg, MachineInstr &MI) {
// immediately prior to pruning.
auto RC = MRI.getRegClass(Reg);
Register R = MRI.createVirtualRegister(RC);
BuildMI(*BB, MI, DebugLoc(), TII->get(TargetOpcode::PHI), R)
.addReg(IllegalPhiDefault.getValue())
.addMBB(PreheaderBB) // Block choice is arbitrary and has no effect.
.addReg(LoopReg)
.addMBB(BB); // Block choice is arbitrary and has no effect.
MachineInstr *IllegalPhi =
BuildMI(*BB, MI, DebugLoc(), TII->get(TargetOpcode::PHI), R)
.addReg(IllegalPhiDefault.getValue())
.addMBB(PreheaderBB) // Block choice is arbitrary and has no effect.
.addReg(LoopReg)
.addMBB(BB); // Block choice is arbitrary and has no effect.
// Illegal phi should belong to the producer stage so that it can be
// filtered correctly during peeling.
S.setStage(IllegalPhi, LoopProducerStage);
return R;
}

57
test/CodeGen/Hexagon/swp-epilog-phi13.ll Normal file
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@ -0,0 +1,57 @@
; RUN: llc -march=hexagon -hexagon-initial-cfg-cleanup=0 -pipeliner-experimental-cg=true < %s | FileCheck %s
; Test epilogue generation when reading loop-carried dependency in stage 1 from
; stage 0. Make sure the illegal phi the expender creates gets cleaned up
; correctly during peeling
; CHECK: loop0
; CHECK: [[REG0:r([0-9]+)]] = add(r{{[0-9]+}},#8)
; CHECK: memw([[REG0]]+#0)
; CHECK: endloop0
; Function Attrs: nounwind
define i32* @f0(i16* nocapture readonly %a0, i32 %a1, i32 %a2, i32 %a3, i16* %b) #0 {
b0:
br i1 undef, label %b1, label %b3
b1: ; preds = %b0
br label %b2
b2: ; preds = %b2, %b1
%v1 = phi i16* [ %a0, %b1 ], [ %v2, %b2 ]
%v2 = phi i16* [ undef, %b1 ], [ %v15, %b2 ]
%v3 = phi i32* [ null, %b1 ], [ %v4, %b2 ]
%v4 = phi i32* [ null, %b1 ], [ %v14, %b2 ]
%v5 = phi i32 [ 0, %b1 ], [ %v13, %b2 ]
%v6 = phi i16* [ undef, %b1 ], [ %v12, %b2 ]
%a = mul i32 %v5, %a2
%add = getelementptr inbounds i16, i16* %b, i32 %a
%v7 = load i16, i16* %add, align 2
%v8 = sext i16 %v7 to i32
%v9 = call i32 @llvm.hexagon.M2.mpy.ll.s0(i32 %v8, i32 %v8) #2
%v92 = call i32 @llvm.hexagon.M2.mpy.ll.s0(i32 %v9, i32 %v9) #2
%v93 = call i32 @llvm.hexagon.M2.mpy.ll.s0(i32 %v92, i32 %v92) #2
%v11 = call i32 @llvm.hexagon.M2.mpy.acc.sat.ll.s0(i32 %v8, i32 undef, i32 undef) #2
store i32 %v11, i32* %v4, align 4
%v12 = getelementptr inbounds i16, i16* %v6, i32 -1
%v13 = add i32 %v5, 1
%v14 = getelementptr inbounds i32, i32* %v3, i32 2
store i32 %v93, i32* %v14, align 4
%v15 = getelementptr inbounds i16, i16* %v1, i32 2
%v16 = icmp slt i32 %v13, %a1
br i1 %v16, label %b2, label %b3
b3: ; preds = %b2, %b0
%out = phi i32* [ null, %b0 ], [ %v14, %b2 ]
ret i32* %out
}
; Function Attrs: nounwind readnone
declare i32 @llvm.hexagon.M2.mpy.ll.s0(i32, i32) #1
; Function Attrs: nounwind readnone
declare i32 @llvm.hexagon.M2.mpy.acc.sat.ll.s0(i32, i32, i32) #1
attributes #0 = { nounwind "target-cpu"="hexagonv60" }
attributes #1 = { nounwind readnone }
attributes #2 = { nounwind }