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[DAGCombine] Add hook to allow target specific test for sqrt input 

PowerPC has instruction ftsqrt/xstsqrtdp etc to do the input test for software square root.
LLVM now tests it with smallest normalized value using abs + setcc. We should add hook to
target that has test instructions.

Reviewed By: Spatel, Chen Zheng, Qiu Chao Fang

Differential Revision: https://reviews.llvm.org/D80706
This commit is contained in:
QingShan Zhang 2020-11-25 05:37:15 +00:00
parent 2c7870dcca
commit 9c588f53fc
9 changed files with 95 additions and 52 deletions
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9
llvm/include/llvm/CodeGen/TargetLowering.h
View File

@ -4277,6 +4277,15 @@ public:
return SDValue();
}
/// Return a target-dependent comparison result if the input operand is
/// suitable for use with a square root estimate calculation. For example, the
/// comparison may check if the operand is NAN, INF, zero, normal, etc. The
/// result should be used as the condition operand for a select or branch.
virtual SDValue getSqrtInputTest(SDValue Operand, SelectionDAG &DAG,
const DenormalMode &Mode) const {
return SDValue();
}
//===--------------------------------------------------------------------===//
// Legalization utility functions
//

39
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -22056,26 +22056,31 @@ SDValue DAGCombiner::buildSqrtEstimateImpl(SDValue Op, SDNodeFlags Flags,
// possibly a denormal. Force the answer to 0.0 for those cases.
SDLoc DL(Op);
EVT CCVT = getSetCCResultType(VT);
ISD::NodeType SelOpcode = VT.isVector() ? ISD::VSELECT : ISD::SELECT;
SDValue FPZero = DAG.getConstantFP(0.0, DL, VT);
DenormalMode DenormMode = DAG.getDenormalMode(VT);
if (DenormMode.Input == DenormalMode::IEEE) {
// This is specifically a check for the handling of denormal inputs,
// not the result.
// Try the target specific test first.
SDValue Test = TLI.getSqrtInputTest(Op, DAG, DenormMode);
if (!Test) {
// If no test provided by target, testing it with denormal inputs to
// avoid wrong estimate.
if (DenormMode.Input == DenormalMode::IEEE) {
// This is specifically a check for the handling of denormal inputs,
// not the result.
// fabs(X) < SmallestNormal ? 0.0 : Est
const fltSemantics &FltSem = DAG.EVTToAPFloatSemantics(VT);
APFloat SmallestNorm = APFloat::getSmallestNormalized(FltSem);
SDValue NormC = DAG.getConstantFP(SmallestNorm, DL, VT);
SDValue FPZero = DAG.getConstantFP(0.0, DL, VT);
SDValue Fabs = DAG.getNode(ISD::FABS, DL, VT, Op);
SDValue IsDenorm = DAG.getSetCC(DL, CCVT, Fabs, NormC, ISD::SETLT);
Est = DAG.getNode(SelOpcode, DL, VT, IsDenorm, FPZero, Est);
} else {
// X == 0.0 ? 0.0 : Est
SDValue FPZero = DAG.getConstantFP(0.0, DL, VT);
SDValue IsZero = DAG.getSetCC(DL, CCVT, Op, FPZero, ISD::SETEQ);
Est = DAG.getNode(SelOpcode, DL, VT, IsZero, FPZero, Est);
// Test = fabs(X) < SmallestNormal
const fltSemantics &FltSem = DAG.EVTToAPFloatSemantics(VT);
APFloat SmallestNorm = APFloat::getSmallestNormalized(FltSem);
SDValue NormC = DAG.getConstantFP(SmallestNorm, DL, VT);
SDValue Fabs = DAG.getNode(ISD::FABS, DL, VT, Op);
Test = DAG.getSetCC(DL, CCVT, Fabs, NormC, ISD::SETLT);
} else
// Test = X == 0.0
Test = DAG.getSetCC(DL, CCVT, Op, FPZero, ISD::SETEQ);
}
// Test ? 0.0 : Est
Est = DAG.getNode(Test.getValueType().isVector() ? ISD::VSELECT
: ISD::SELECT,
DL, VT, Test, FPZero, Est);
}
}
return Est;

29
llvm/lib/Target/PowerPC/PPCISelLowering.cpp
View File

@ -1447,6 +1447,8 @@ const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
return "PPCISD::FP_TO_SINT_IN_VSR";
case PPCISD::FRE: return "PPCISD::FRE";
case PPCISD::FRSQRTE: return "PPCISD::FRSQRTE";
case PPCISD::FTSQRT:
return "PPCISD::FTSQRT";
case PPCISD::STFIWX: return "PPCISD::STFIWX";
case PPCISD::VPERM: return "PPCISD::VPERM";
case PPCISD::XXSPLT: return "PPCISD::XXSPLT";
@ -12758,6 +12760,33 @@ static int getEstimateRefinementSteps(EVT VT, const PPCSubtarget &Subtarget) {
return RefinementSteps;
}
SDValue PPCTargetLowering::getSqrtInputTest(SDValue Op, SelectionDAG &DAG,
const DenormalMode &Mode) const {
// TODO - add support for v2f64/v4f32
EVT VT = Op.getValueType();
if (VT != MVT::f64)
return SDValue();
SDLoc DL(Op);
// The output register of FTSQRT is CR field.
SDValue FTSQRT = DAG.getNode(PPCISD::FTSQRT, DL, MVT::i32, Op);
// ftsqrt BF,FRB
// Let e_b be the unbiased exponent of the double-precision
// floating-point operand in register FRB.
// fe_flag is set to 1 if either of the following conditions occurs.
// - The double-precision floating-point operand in register FRB is a zero,
// a NaN, or an infinity, or a negative value.
// - e_b is less than or equal to -970.
// Otherwise fe_flag is set to 0.
// Both VSX and non-VSX versions would set EQ bit in the CR if the number is
// not eligible for iteration. (zero/negative/infinity/nan or unbiased
// exponent is less than -970)
SDValue SRIdxVal = DAG.getTargetConstant(PPC::sub_eq, DL, MVT::i32);
return SDValue(DAG.getMachineNode(TargetOpcode::EXTRACT_SUBREG, DL, MVT::i1,
FTSQRT, SRIdxVal),
0);
}
SDValue PPCTargetLowering::getSqrtEstimate(SDValue Operand, SelectionDAG &DAG,
int Enabled, int &RefinementSteps,
bool &UseOneConstNR,

5
llvm/lib/Target/PowerPC/PPCISelLowering.h
View File

@ -89,6 +89,9 @@ namespace llvm {
FRE,
FRSQRTE,
/// Test instruction for software square root.
FTSQRT,
/// VPERM - The PPC VPERM Instruction.
///
VPERM,
@ -1283,6 +1286,8 @@ namespace llvm {
bool Reciprocal) const override;
SDValue getRecipEstimate(SDValue Operand, SelectionDAG &DAG, int Enabled,
int &RefinementSteps) const override;
SDValue getSqrtInputTest(SDValue Operand, SelectionDAG &DAG,
const DenormalMode &Mode) const override;
unsigned combineRepeatedFPDivisors() const override;
SDValue

3
llvm/lib/Target/PowerPC/PPCInstrFormats.td
View File

@ -637,9 +637,10 @@ class XForm_17<bits<6> opcode, bits<10> xo, dag OOL, dag IOL, string asmstr,
}
class XForm_17a<bits<6> opcode, bits<10> xo, dag OOL, dag IOL, string asmstr,
InstrItinClass itin>
InstrItinClass itin, list<dag> pattern>
: XForm_17<opcode, xo, OOL, IOL, asmstr, itin > {
let FRA = 0;
let Pattern = pattern;
}
class XForm_18<bits<6> opcode, bits<10> xo, dag OOL, dag IOL, string asmstr,

7
llvm/lib/Target/PowerPC/PPCInstrInfo.td
View File

@ -74,6 +74,9 @@ def SDT_PPCcondbr : SDTypeProfile<0, 3, [
SDTCisVT<0, i32>, SDTCisVT<2, OtherVT>
]>;
def SDT_PPCFtsqrt : SDTypeProfile<1, 1, [
SDTCisVT<0, i32>]>;
def SDT_PPClbrx : SDTypeProfile<1, 2, [
SDTCisInt<0>, SDTCisPtrTy<1>, SDTCisVT<2, OtherVT>
]>;
@ -124,6 +127,7 @@ def SDT_PPCFPMinMax : SDTypeProfile<1, 2, [
def PPCfre : SDNode<"PPCISD::FRE", SDTFPUnaryOp, []>;
def PPCfrsqrte: SDNode<"PPCISD::FRSQRTE", SDTFPUnaryOp, []>;
def PPCftsqrt : SDNode<"PPCISD::FTSQRT", SDT_PPCFtsqrt,[]>;
def PPCfcfid : SDNode<"PPCISD::FCFID", SDTFPUnaryOp, []>;
def PPCfcfidu : SDNode<"PPCISD::FCFIDU", SDTFPUnaryOp, []>;
@ -2643,7 +2647,8 @@ let isCompare = 1, mayRaiseFPException = 1, hasSideEffects = 0 in {
def FTDIV: XForm_17<63, 128, (outs crrc:$crD), (ins f8rc:$fA, f8rc:$fB),
"ftdiv $crD, $fA, $fB", IIC_FPCompare>;
def FTSQRT: XForm_17a<63, 160, (outs crrc:$crD), (ins f8rc:$fB),
"ftsqrt $crD, $fB", IIC_FPCompare>;
"ftsqrt $crD, $fB", IIC_FPCompare,
[(set i32:$crD, (PPCftsqrt f64:$fB))]>;
let mayRaiseFPException = 1, hasSideEffects = 0 in {
let Interpretation64Bit = 1, isCodeGenOnly = 1 in

3
llvm/lib/Target/PowerPC/PPCInstrVSX.td
View File

@ -629,7 +629,8 @@ let hasSideEffects = 0 in {
"xstdivdp $crD, $XA, $XB", IIC_FPCompare, []>;
def XSTSQRTDP : XX2Form_1<60, 106,
(outs crrc:$crD), (ins vsfrc:$XB),
"xstsqrtdp $crD, $XB", IIC_FPCompare, []>;
"xstsqrtdp $crD, $XB", IIC_FPCompare,
[(set i32:$crD, (PPCftsqrt f64:$XB))]>;
def XVTDIVDP : XX3Form_1<60, 125,
(outs crrc:$crD), (ins vsrc:$XA, vsrc:$XB),
"xvtdivdp $crD, $XA, $XB", IIC_FPCompare, []>;

7
llvm/test/CodeGen/PowerPC/fma-mutate.ll
View File

@ -9,12 +9,9 @@ declare double @llvm.sqrt.f64(double)
define double @foo3_fmf(double %a) nounwind {
; CHECK-LABEL: foo3_fmf:
; CHECK: # %bb.0:
; CHECK-NEXT: xsabsdp 0, 1
; CHECK-NEXT: addis 3, 2, .LCPI0_2@toc@ha
; CHECK-NEXT: lfd 2, .LCPI0_2@toc@l(3)
; CHECK-NEXT: xscmpudp 0, 0, 2
; CHECK-NEXT: xstsqrtdp 0, 1
; CHECK-NEXT: xxlxor 0, 0, 0
; CHECK-NEXT: blt 0, .LBB0_2
; CHECK-NEXT: bc 12, 2, .LBB0_2
; CHECK-NEXT: # %bb.1:
; CHECK-NEXT: xsrsqrtedp 0, 1
; CHECK-NEXT: addis 3, 2, .LCPI0_0@toc@ha

45
llvm/test/CodeGen/PowerPC/recipest.ll
View File

@ -749,11 +749,8 @@ define <4 x float> @hoo2_safe(<4 x float> %a, <4 x float> %b) nounwind {
define double @foo3_fmf(double %a) nounwind {
; CHECK-P7-LABEL: foo3_fmf:
; CHECK-P7: # %bb.0:
; CHECK-P7-NEXT: fabs 0, 1
; CHECK-P7-NEXT: addis 3, 2, .LCPI20_2@toc@ha
; CHECK-P7-NEXT: lfd 2, .LCPI20_2@toc@l(3)
; CHECK-P7-NEXT: fcmpu 0, 0, 2
; CHECK-P7-NEXT: blt 0, .LBB20_2
; CHECK-P7-NEXT: ftsqrt 0, 1
; CHECK-P7-NEXT: bc 12, 2, .LBB20_2
; CHECK-P7-NEXT: # %bb.1:
; CHECK-P7-NEXT: frsqrte 0, 1
; CHECK-P7-NEXT: addis 3, 2, .LCPI20_0@toc@ha
@ -770,18 +767,15 @@ define double @foo3_fmf(double %a) nounwind {
; CHECK-P7-NEXT: fmul 1, 1, 0
; CHECK-P7-NEXT: blr
; CHECK-P7-NEXT: .LBB20_2:
; CHECK-P7-NEXT: addis 3, 2, .LCPI20_3@toc@ha
; CHECK-P7-NEXT: lfs 1, .LCPI20_3@toc@l(3)
; CHECK-P7-NEXT: addis 3, 2, .LCPI20_2@toc@ha
; CHECK-P7-NEXT: lfs 1, .LCPI20_2@toc@l(3)
; CHECK-P7-NEXT: blr
;
; CHECK-P8-LABEL: foo3_fmf:
; CHECK-P8: # %bb.0:
; CHECK-P8-NEXT: xsabsdp 0, 1
; CHECK-P8-NEXT: addis 3, 2, .LCPI20_2@toc@ha
; CHECK-P8-NEXT: lfd 2, .LCPI20_2@toc@l(3)
; CHECK-P8-NEXT: xscmpudp 0, 0, 2
; CHECK-P8-NEXT: xstsqrtdp 0, 1
; CHECK-P8-NEXT: xxlxor 0, 0, 0
; CHECK-P8-NEXT: blt 0, .LBB20_2
; CHECK-P8-NEXT: bc 12, 2, .LBB20_2
; CHECK-P8-NEXT: # %bb.1:
; CHECK-P8-NEXT: xsrsqrtedp 0, 1
; CHECK-P8-NEXT: addis 3, 2, .LCPI20_0@toc@ha
@ -803,12 +797,9 @@ define double @foo3_fmf(double %a) nounwind {
;
; CHECK-P9-LABEL: foo3_fmf:
; CHECK-P9: # %bb.0:
; CHECK-P9-NEXT: addis 3, 2, .LCPI20_2@toc@ha
; CHECK-P9-NEXT: xsabsdp 0, 1
; CHECK-P9-NEXT: lfd 2, .LCPI20_2@toc@l(3)
; CHECK-P9-NEXT: xscmpudp 0, 0, 2
; CHECK-P9-NEXT: xstsqrtdp 0, 1
; CHECK-P9-NEXT: xxlxor 0, 0, 0
; CHECK-P9-NEXT: blt 0, .LBB20_2
; CHECK-P9-NEXT: bc 12, 2, .LBB20_2
; CHECK-P9-NEXT: # %bb.1:
; CHECK-P9-NEXT: xsrsqrtedp 0, 1
; CHECK-P9-NEXT: addis 3, 2, .LCPI20_0@toc@ha
@ -1038,18 +1029,18 @@ define <2 x double> @hoo4_fmf(<2 x double> %a) #1 {
; CHECK-P7-LABEL: hoo4_fmf:
; CHECK-P7: # %bb.0:
; CHECK-P7-NEXT: addis 3, 2, .LCPI26_2@toc@ha
; CHECK-P7-NEXT: ftsqrt 0, 1
; CHECK-P7-NEXT: fmr 3, 1
; CHECK-P7-NEXT: addis 4, 2, .LCPI26_1@toc@ha
; CHECK-P7-NEXT: addis 4, 2, .LCPI26_0@toc@ha
; CHECK-P7-NEXT: lfs 0, .LCPI26_2@toc@l(3)
; CHECK-P7-NEXT: addis 3, 2, .LCPI26_0@toc@ha
; CHECK-P7-NEXT: lfs 4, .LCPI26_1@toc@l(4)
; CHECK-P7-NEXT: lfs 5, .LCPI26_0@toc@l(3)
; CHECK-P7-NEXT: fcmpu 0, 1, 0
; CHECK-P7-NEXT: addis 3, 2, .LCPI26_1@toc@ha
; CHECK-P7-NEXT: lfs 5, .LCPI26_0@toc@l(4)
; CHECK-P7-NEXT: lfs 4, .LCPI26_1@toc@l(3)
; CHECK-P7-NEXT: fmr 1, 0
; CHECK-P7-NEXT: bne 0, .LBB26_3
; CHECK-P7-NEXT: bc 4, 2, .LBB26_3
; CHECK-P7-NEXT: # %bb.1:
; CHECK-P7-NEXT: fcmpu 0, 2, 0
; CHECK-P7-NEXT: bne 0, .LBB26_4
; CHECK-P7-NEXT: ftsqrt 0, 2
; CHECK-P7-NEXT: bc 4, 2, .LBB26_4
; CHECK-P7-NEXT: .LBB26_2:
; CHECK-P7-NEXT: fmr 2, 0
; CHECK-P7-NEXT: blr
@ -1063,8 +1054,8 @@ define <2 x double> @hoo4_fmf(<2 x double> %a) #1 {
; CHECK-P7-NEXT: fmadd 1, 3, 1, 5
; CHECK-P7-NEXT: fmul 3, 3, 4
; CHECK-P7-NEXT: fmul 1, 3, 1
; CHECK-P7-NEXT: fcmpu 0, 2, 0
; CHECK-P7-NEXT: beq 0, .LBB26_2
; CHECK-P7-NEXT: ftsqrt 0, 2
; CHECK-P7-NEXT: bc 12, 2, .LBB26_2
; CHECK-P7-NEXT: .LBB26_4:
; CHECK-P7-NEXT: frsqrte 0, 2
; CHECK-P7-NEXT: fmul 3, 2, 0