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[AArch64] Codegen VMAX/VMIN for safe math cases

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237247 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Artyom Skrobov 2015-05-13 12:01:09 +00:00
parent 66112dd7f8
commit e8dceea402
3 changed files with 94 additions and 44 deletions
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112
lib/Target/AArch64/AArch64ISelLowering.cpp
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@ -491,6 +491,7 @@ AArch64TargetLowering::AArch64TargetLowering(const TargetMachine &TM,
setTargetDAGCombine(ISD::SELECT);
setTargetDAGCombine(ISD::VSELECT);
setTargetDAGCombine(ISD::SELECT_CC);
setTargetDAGCombine(ISD::INTRINSIC_VOID);
setTargetDAGCombine(ISD::INTRINSIC_W_CHAIN);
@ -3701,46 +3702,6 @@ SDValue AArch64TargetLowering::LowerSELECT_CC(ISD::CondCode CC, SDValue LHS,
assert(LHS.getValueType() == MVT::f32 || LHS.getValueType() == MVT::f64);
assert(LHS.getValueType() == RHS.getValueType());
EVT VT = TVal.getValueType();
// Try to match this select into a max/min operation, which have dedicated
// opcode in the instruction set.
// FIXME: This is not correct in the presence of NaNs, so we only enable this
// in no-NaNs mode.
if (getTargetMachine().Options.NoNaNsFPMath) {
SDValue MinMaxLHS = TVal, MinMaxRHS = FVal;
if (selectCCOpsAreFMaxCompatible(LHS, MinMaxRHS) &&
selectCCOpsAreFMaxCompatible(RHS, MinMaxLHS)) {
CC = ISD::getSetCCSwappedOperands(CC);
std::swap(MinMaxLHS, MinMaxRHS);
}
if (selectCCOpsAreFMaxCompatible(LHS, MinMaxLHS) &&
selectCCOpsAreFMaxCompatible(RHS, MinMaxRHS)) {
switch (CC) {
default:
break;
case ISD::SETGT:
case ISD::SETGE:
case ISD::SETUGT:
case ISD::SETUGE:
case ISD::SETOGT:
case ISD::SETOGE:
return DAG.getNode(AArch64ISD::FMAX, dl, VT, MinMaxLHS, MinMaxRHS);
break;
case ISD::SETLT:
case ISD::SETLE:
case ISD::SETULT:
case ISD::SETULE:
case ISD::SETOLT:
case ISD::SETOLE:
return DAG.getNode(AArch64ISD::FMIN, dl, VT, MinMaxLHS, MinMaxRHS);
break;
}
}
}
// If that fails, we'll need to perform an FCMP + CSEL sequence. Go ahead
// and do the comparison.
SDValue Cmp = emitComparison(LHS, RHS, CC, dl, DAG);
// Unfortunately, the mapping of LLVM FP CC's onto AArch64 CC's isn't totally
@ -8735,6 +8696,75 @@ static SDValue performSelectCombine(SDNode *N,
return DAG.getSelect(DL, ResVT, Mask, N->getOperand(1), N->getOperand(2));
}
/// performSelectCCCombine - Target-specific DAG combining for ISD::SELECT_CC
/// to match FMIN/FMAX patterns.
static SDValue performSelectCCCombine(SDNode *N, SelectionDAG &DAG) {
// Try to use FMIN/FMAX instructions for FP selects like "x < y ? x : y".
// Unless the NoNaNsFPMath option is set, be careful about NaNs:
// vmax/vmin return NaN if either operand is a NaN;
// only do the transformation when it matches that behavior.
SDValue CondLHS = N->getOperand(0);
SDValue CondRHS = N->getOperand(1);
SDValue LHS = N->getOperand(2);
SDValue RHS = N->getOperand(3);
ISD::CondCode CC = cast<CondCodeSDNode>(N->getOperand(4))->get();
unsigned Opcode;
bool IsReversed;
if (selectCCOpsAreFMaxCompatible(CondLHS, LHS) &&
selectCCOpsAreFMaxCompatible(CondRHS, RHS)) {
IsReversed = false; // x CC y ? x : y
} else if (selectCCOpsAreFMaxCompatible(CondRHS, LHS) &&
selectCCOpsAreFMaxCompatible(CondLHS, RHS)) {
IsReversed = true ; // x CC y ? y : x
} else {
return SDValue();
}
bool IsUnordered = false, IsOrEqual;
switch (CC) {
default:
return SDValue();
case ISD::SETULT:
case ISD::SETULE:
IsUnordered = true;
case ISD::SETOLT:
case ISD::SETOLE:
case ISD::SETLT:
case ISD::SETLE:
IsOrEqual = (CC == ISD::SETLE || CC == ISD::SETOLE || CC == ISD::SETULE);
Opcode = IsReversed ? AArch64ISD::FMAX : AArch64ISD::FMIN;
break;
case ISD::SETUGT:
case ISD::SETUGE:
IsUnordered = true;
case ISD::SETOGT:
case ISD::SETOGE:
case ISD::SETGT:
case ISD::SETGE:
IsOrEqual = (CC == ISD::SETGE || CC == ISD::SETOGE || CC == ISD::SETUGE);
Opcode = IsReversed ? AArch64ISD::FMIN : AArch64ISD::FMAX;
break;
}
// If LHS is NaN, an ordered comparison will be false and the result will be
// the RHS, but FMIN(NaN, RHS) = FMAX(NaN, RHS) = NaN. Avoid this by checking
// that LHS != NaN. Likewise, for unordered comparisons, check for RHS != NaN.
if (!DAG.isKnownNeverNaN(IsUnordered ? RHS : LHS))
return SDValue();
// For xxx-or-equal comparisons, "+0 <= -0" and "-0 >= +0" will both be true,
// but FMIN will return -0, and FMAX will return +0. So FMIN/FMAX can only be
// used for unsafe math or if one of the operands is known to be nonzero.
if (IsOrEqual && !DAG.getTarget().Options.UnsafeFPMath &&
!(DAG.isKnownNeverZero(LHS) || DAG.isKnownNeverZero(RHS)))
return SDValue();
return DAG.getNode(Opcode, SDLoc(N), N->getValueType(0), LHS, RHS);
}
SDValue AArch64TargetLowering::PerformDAGCombine(SDNode *N,
DAGCombinerInfo &DCI) const {
SelectionDAG &DAG = DCI.DAG;
@ -8767,6 +8797,8 @@ SDValue AArch64TargetLowering::PerformDAGCombine(SDNode *N,
return performSelectCombine(N, DCI);
case ISD::VSELECT:
return performVSelectCombine(N, DCI.DAG);
case ISD::SELECT_CC:
return performSelectCCCombine(N, DCI.DAG);
case ISD::STORE:
return performSTORECombine(N, DCI, DAG, Subtarget);
case AArch64ISD::BRCOND:

3
lib/Target/ARM/ARMISelLowering.cpp
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@ -3521,9 +3521,6 @@ SDValue ARMTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
// c = fcmp [?gt, ?ge, ?lt, ?le] a, b
// select c, a, b
// In NoNaNsFPMath the CC will have been changed from, e.g., 'ogt' to 'gt'.
// FIXME: There is similar code that allows some extensions in
// AArch64TargetLowering::LowerSELECT_CC that should be shared with this
// code.
bool swapSides = false;
if (!getTargetMachine().Options.NoNaNsFPMath) {
// transformability may depend on which way around we compare

23
test/CodeGen/AArch64/arm64-fmax.ll
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@ -1,29 +1,49 @@
; RUN: llc -march=arm64 -enable-no-nans-fp-math < %s | FileCheck %s
; RUN: llc -march=arm64 < %s | FileCheck %s --check-prefix=CHECK-SAFE
define double @test_direct(float %in) #1 {
; CHECK-LABEL: test_direct:
; CHECK-SAFE-LABEL: test_direct:
%cmp = fcmp olt float %in, 0.000000e+00
%longer = fpext float %in to double
%val = select i1 %cmp, double 0.000000e+00, double %longer
ret double %val
; CHECK: fmax
; CHECK-SAFE: fmax
}
define double @test_cross(float %in) #1 {
; CHECK-LABEL: test_cross:
; CHECK-SAFE-LABEL: test_cross:
%cmp = fcmp ult float %in, 0.000000e+00
%longer = fpext float %in to double
%val = select i1 %cmp, double %longer, double 0.000000e+00
ret double %val
; CHECK: fmin
; CHECK-SAFE: fmin
}
; Same as previous, but with ordered comparison;
; can't be converted in safe-math mode.
define double @test_cross_fail_nan(float %in) #1 {
; CHECK-LABEL: test_cross_fail_nan:
; CHECK-SAFE-LABEL: test_cross_fail_nan:
%cmp = fcmp olt float %in, 0.000000e+00
%longer = fpext float %in to double
%val = select i1 %cmp, double %longer, double 0.000000e+00
ret double %val
; CHECK: fmin
; CHECK-SAFE: fcsel d0, d1, d0, mi
}
; This isn't a min or a max, but passes the first condition for swapping the
; results. Make sure they're put back before we resort to the normal fcsel.
define float @test_cross_fail(float %lhs, float %rhs) {
; CHECK-LABEL: test_cross_fail:
; CHECK-SAFE-LABEL: test_cross_fail:
%tst = fcmp une float %lhs, %rhs
%res = select i1 %tst, float %rhs, float %lhs
ret float %res
@ -31,4 +51,5 @@ define float @test_cross_fail(float %lhs, float %rhs) {
; The register allocator would have to decide to be deliberately obtuse before
; other register were used.
; CHECK: fcsel s0, s1, s0, ne
}
; CHECK-SAFE: fcsel s0, s1, s0, ne
}