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[PowerPC] Fix the PPCInstrInfo::getInstrLatency implementation 

PowerPC uses itineraries to describe processor pipelines (and dispatch-group
restrictions for P7/P8 cores). Unfortunately, the target-independent
implementation of TII.getInstrLatency calls ItinData->getStageLatency, and that
looks for the largest cycle count in the pipeline for any given instruction.
This, however, yields the wrong answer for the PPC itineraries, because we
don't encode the full pipeline. Because the functional units are fully
pipelined, we only model the initial stages (there are no relevant hazards in
the later stages to model), and so the technique employed by getStageLatency
does not really work. Instead, we should take the maximum output operand
latency, and that's what PPCInstrInfo::getInstrLatency now does.

This caused some test-case churn, including two unfortunate side effects.
First, the new arrangement of copies we get from function parameters now
sometimes blocks VSX FMA mutation (a FIXME has been added to the code and the
test cases), and we have one significant test-suite regression:

SingleSource/Benchmarks/BenchmarkGame/spectral-norm
	56.4185% +/- 18.9398%

In this benchmark we have a loop with a vectorized FP divide, and it with the
new scheduling both divides end up in the same dispatch group (which in this
case seems to cause a problem, although why is not exactly clear). The grouping
structure is hard to predict from the bottom of the loop, and there may not be
much we can do to fix this.

Very few other test-suite performance effects were really significant, but
almost all weakly favor this change. However, in light of the issues
highlighted above, I've left the old behavior available via a
command-line flag.

llvm-svn: 242188
This commit is contained in:
Hal Finkel 2015-07-14 20:02:02 +00:00
parent 7fa38a5349
commit 8acae5276e
12 changed files with 96 additions and 34 deletions
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33
llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
View File

@ -57,6 +57,10 @@ static cl::opt<bool> VSXSelfCopyCrash("crash-on-ppc-vsx-self-copy",
cl::desc("Causes the backend to crash instead of generating a nop VSX copy"),
cl::Hidden);
static cl::opt<bool>
UseOldLatencyCalc("ppc-old-latency-calc", cl::Hidden,
cl::desc("Use the old (incorrect) instruction latency calculation"));
// Pin the vtable to this file.
void PPCInstrInfo::anchor() {}
@ -103,6 +107,35 @@ PPCInstrInfo::CreateTargetPostRAHazardRecognizer(const InstrItineraryData *II,
return new ScoreboardHazardRecognizer(II, DAG);
}
unsigned PPCInstrInfo::getInstrLatency(const InstrItineraryData *ItinData,
const MachineInstr *MI,
unsigned *PredCost) const {
if (!ItinData || UseOldLatencyCalc)
return PPCGenInstrInfo::getInstrLatency(ItinData, MI, PredCost);
// The default implementation of getInstrLatency calls getStageLatency, but
// getStageLatency does not do the right thing for us. While we have
// itinerary, most cores are fully pipelined, and so the itineraries only
// express the first part of the pipeline, not every stage. Instead, we need
// to use the listed output operand cycle number (using operand 0 here, which
// is an output).
unsigned Latency = 1;
unsigned DefClass = MI->getDesc().getSchedClass();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isDef() || MO.isImplicit())
continue;
int Cycle = ItinData->getOperandCycle(DefClass, i);
if (Cycle < 0)
continue;
Latency = std::max(Latency, (unsigned) Cycle);
}
return Latency;
}
int PPCInstrInfo::getOperandLatency(const InstrItineraryData *ItinData,
const MachineInstr *DefMI, unsigned DefIdx,

4
llvm/lib/Target/PowerPC/PPCInstrInfo.h
View File

@ -95,6 +95,10 @@ public:
CreateTargetPostRAHazardRecognizer(const InstrItineraryData *II,
const ScheduleDAG *DAG) const override;
unsigned getInstrLatency(const InstrItineraryData *ItinData,
const MachineInstr *MI,
unsigned *PredCost = nullptr) const override;
int getOperandLatency(const InstrItineraryData *ItinData,
const MachineInstr *DefMI, unsigned DefIdx,
const MachineInstr *UseMI,

4
llvm/lib/Target/PowerPC/PPCScheduleP7.td
View File

@ -315,6 +315,10 @@ def P7Itineraries : ProcessorItineraries<
P7_DU3, P7_DU4], 0>,
InstrStage<1, [P7_VS1, P7_VS2]>],
[5, 1, 1]>,
InstrItinData<IIC_FPAddSub , [InstrStage<1, [P7_DU1, P7_DU2,
P7_DU3, P7_DU4], 0>,
InstrStage<1, [P7_VS1, P7_VS2]>],
[5, 1, 1]>,
InstrItinData<IIC_FPCompare , [InstrStage<1, [P7_DU1, P7_DU2,
P7_DU3, P7_DU4], 0>,
InstrStage<1, [P7_VS1, P7_VS2]>],

4
llvm/lib/Target/PowerPC/PPCScheduleP8.td
View File

@ -323,6 +323,10 @@ def P8Itineraries : ProcessorItineraries<
P8_DU4, P8_DU5, P8_DU6], 0>,
InstrStage<1, [P8_FPU1, P8_FPU2]>],
[5, 1, 1]>,
InstrItinData<IIC_FPAddSub , [InstrStage<1, [P8_DU1, P8_DU2, P8_DU3,
P8_DU4, P8_DU5, P8_DU6], 0>,
InstrStage<1, [P8_FPU1, P8_FPU2]>],
[5, 1, 1]>,
InstrItinData<IIC_FPCompare , [InstrStage<1, [P8_DU1, P8_DU2, P8_DU3,
P8_DU4, P8_DU5, P8_DU6], 0>,
InstrStage<1, [P8_FPU1, P8_FPU2]>],

10
llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp
View File

@ -136,6 +136,16 @@ protected:
// source of the copy, it must still be live here. We can't use
// interval testing for a physical register, so as long as we're
// walking the MIs we may as well test liveness here.
//
// FIXME: There is a case that occurs in practice, like this:
// %vreg9<def> = COPY %F1; VSSRC:%vreg9
// ...
// %vreg6<def> = COPY %vreg9; VSSRC:%vreg6,%vreg9
// %vreg7<def> = COPY %vreg9; VSSRC:%vreg7,%vreg9
// %vreg9<def,tied1> = XSMADDASP %vreg9<tied0>, %vreg1, %vreg4; VSSRC:
// %vreg6<def,tied1> = XSMADDASP %vreg6<tied0>, %vreg1, %vreg2; VSSRC:
// %vreg7<def,tied1> = XSMADDASP %vreg7<tied0>, %vreg1, %vreg3; VSSRC:
// which prevents an otherwise-profitable transformation.
bool OtherUsers = false, KillsAddendSrc = false;
for (auto J = std::prev(I), JE = MachineBasicBlock::iterator(AddendMI);
J != JE; --J) {

4
llvm/test/CodeGen/PowerPC/ppc-crbits-onoff.ll
View File

@ -15,8 +15,8 @@ entry:
; CHECK-DAG: cmplwi {{[0-9]+}}, 3, 0
; CHECK-DAG: li [[REG2:[0-9]+]], 1
; CHECK-DAG: cntlzw [[REG3:[0-9]+]],
; CHECK: isel 3, 0, [[REG2]]
; CHECK: and 3, 3, [[REG3]]
; CHECK: isel [[REG4:[0-9]+]], 0, [[REG2]]
; CHECK: and 3, [[REG4]], [[REG3]]
; CHECK: blr
}

6
llvm/test/CodeGen/PowerPC/ppc64-fastcc-fast-isel.ll
View File

@ -35,7 +35,7 @@ define fastcc double @f2(i64 %g1, double %f1, i64 %g2, double %f2, i64 %g3, doub
}
define void @cg2(i64 %v) #0 {
tail call fastcc i64 @g1(i64 0, double 0.0, i64 %v, double 0.0, i64 0, double 0.0, i64 0, double 0.0)
call fastcc i64 @g1(i64 0, double 0.0, i64 %v, double 0.0, i64 0, double 0.0, i64 0, double 0.0)
ret void
; CHECK-LABEL: @cg2
@ -44,11 +44,11 @@ define void @cg2(i64 %v) #0 {
}
define void @cf2(double %v) #0 {
tail call fastcc i64 @g1(i64 0, double 0.0, i64 0, double %v, i64 0, double 0.0, i64 0, double 0.0)
call fastcc i64 @g1(i64 0, double 0.0, i64 0, double %v, i64 0, double 0.0, i64 0, double 0.0)
ret void
; CHECK-LABEL: @cf2
; CHECK: mr 2, 1
; CHECK: fmr 2, 1
; CHECK: blr
}

10
llvm/test/CodeGen/PowerPC/ppc64-fastcc.ll
View File

@ -521,8 +521,9 @@ define void @cv13(<4 x i32> %v) #0 {
ret void
; CHECK-LABEL: @cv13
; CHECK: li [[REG1:[0-9]+]], 96
; CHECK: stvx 2, 1, [[REG1]]
; CHECK-DAG: li [[REG1:[0-9]+]], 96
; CHECK-DAG: vor [[REG2:[0-9]+]], 2, 2
; CHECK: stvx [[REG2]], 1, [[REG1]]
; CHECK: blr
}
@ -531,8 +532,9 @@ define void @cv14(<4 x i32> %v) #0 {
ret void
; CHECK-LABEL: @cv14
; CHECK: li [[REG1:[0-9]+]], 128
; CHECK: stvx 2, 1, [[REG1]]
; CHECK-DAG: li [[REG1:[0-9]+]], 128
; CHECK-DAG: vor [[REG2:[0-9]+]], 2, 2
; CHECK: stvx [[REG2]], 1, [[REG1]]
; CHECK: blr
}

8
llvm/test/CodeGen/PowerPC/sjlj.ll
View File

@ -18,10 +18,10 @@ entry:
; CHECK: addi [[REG]], [[REG]], env_sigill@toc@l
; CHECK: ld 31, 0([[REG]])
; CHECK: ld [[REG2:[0-9]+]], 8([[REG]])
; CHECK: ld 1, 16([[REG]])
; CHECK: mtctr [[REG2]]
; CHECK: ld 30, 32([[REG]])
; CHECK: ld 2, 24([[REG]])
; CHECK-DAG: ld 1, 16([[REG]])
; CHECK-DAG: mtctr [[REG2]]
; CHECK-DAG: ld 30, 32([[REG]])
; CHECK-DAG: ld 2, 24([[REG]])
; CHECK: bctr
return: ; No predecessors!

4
llvm/test/CodeGen/PowerPC/tls-store2.ll
View File

@ -29,6 +29,8 @@ entry:
; CHECK: addi 3, {{[0-9]+}}, __once_call@got@tlsgd@l
; CHECK: bl __tls_get_addr(__once_call@tlsgd)
; CHECK-NEXT: nop
; CHECK: std {{[0-9]+}}, 0(3)
; FIXME: We don't really need the copy here either, we could move the store up.
; CHECK: mr [[REG1:[0-9]+]], 3
; CHECK: std {{[0-9]+}}, 0([[REG1]])
declare void @__once_call_impl()

30
llvm/test/CodeGen/PowerPC/vsx-fma-m.ll
View File

@ -49,12 +49,13 @@ entry:
; CHECK-LABEL: @test2
; CHECK-DAG: li [[C1:[0-9]+]], 8
; CHECK-DAG: li [[C2:[0-9]+]], 16
; CHECK-DAG: xsmaddmdp 3, 2, 1
; CHECK-DAG: xsmaddmdp 4, 2, 1
; CHECK-DAG: xsmaddadp 1, 2, 5
; CHECK-DAG: stxsdx 3, 0, 8
; CHECK-DAG: stxsdx 4, 8, [[C1]]
; CHECK-DAG: stxsdx 1, 8, [[C2]]
; FIXME: We no longer get this because of copy ordering at the MI level.
; CHECX-DAG: xsmaddmdp 3, 2, 1
; CHECX-DAG: xsmaddmdp 4, 2, 1
; CHECX-DAG: xsmaddadp 1, 2, 5
; CHECX-DAG: stxsdx 3, 0, 8
; CHECX-DAG: stxsdx 4, 8, [[C1]]
; CHECX-DAG: stxsdx 1, 8, [[C2]]
; CHECK: blr
; CHECK-FISL-LABEL: @test2
@ -213,14 +214,15 @@ entry:
ret void
; CHECK-LABEL: @testv2
; CHECK-DAG: xvmaddmdp 36, 35, 34
; CHECK-DAG: xvmaddmdp 37, 35, 34
; CHECK-DAG: li [[C1:[0-9]+]], 16
; CHECK-DAG: li [[C2:[0-9]+]], 32
; CHECK-DAG: xvmaddadp 34, 35, 38
; CHECK-DAG: stxvd2x 36, 0, 3
; CHECK-DAG: stxvd2x 37, 3, [[C1:[0-9]+]]
; CHECK-DAG: stxvd2x 34, 3, [[C2:[0-9]+]]
; FIXME: We currently don't get this because of copy ordering on the MI level.
; CHECX-DAG: xvmaddmdp 36, 35, 34
; CHECX-DAG: xvmaddmdp 37, 35, 34
; CHECX-DAG: li [[C1:[0-9]+]], 16
; CHECX-DAG: li [[C2:[0-9]+]], 32
; CHECX-DAG: xvmaddadp 34, 35, 38
; CHECX-DAG: stxvd2x 36, 0, 3
; CHECX-DAG: stxvd2x 37, 3, [[C1:[0-9]+]]
; CHECX-DAG: stxvd2x 34, 3, [[C2:[0-9]+]]
; CHECK: blr
; CHECK-FISL-LABEL: @testv2

13
llvm/test/CodeGen/PowerPC/vsx-fma-sp.ll
View File

@ -42,12 +42,13 @@ entry:
; CHECK-LABEL: @test2sp
; CHECK-DAG: li [[C1:[0-9]+]], 4
; CHECK-DAG: li [[C2:[0-9]+]], 8
; CHECK-DAG: xsmaddmsp 3, 2, 1
; CHECK-DAG: xsmaddmsp 4, 2, 1
; CHECK-DAG: xsmaddasp 1, 2, 5
; CHECK-DAG: stxsspx 3, 0, 8
; CHECK-DAG: stxsspx 4, 8, [[C1]]
; CHECK-DAG: stxsspx 1, 8, [[C2]]
; FIXME: We now miss this because of copy ordering at the MI level.
; CHECX-DAG: xsmaddmsp 3, 2, 1
; CHECX-DAG: xsmaddmsp 4, 2, 1
; CHECX-DAG: xsmaddasp 1, 2, 5
; CHECX-DAG: stxsspx 3, 0, 8
; CHECX-DAG: stxsspx 4, 8, [[C1]]
; CHECX-DAG: stxsspx 1, 8, [[C2]]
; CHECK: blr
; CHECK-FISL-LABEL: @test2sp