[llvm] r252839 - LegalizeDAG: Fix and improve FCOPYSIGN/FABS legalization
Matthias Braun via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 11 17:02:47 PST 2015
Author: matze
Date: Wed Nov 11 19:02:47 2015
New Revision: 252839
URL: http://llvm.org/viewvc/llvm-project?rev=252839&view=rev
Log:
LegalizeDAG: Fix and improve FCOPYSIGN/FABS legalization
- Factor out code to query and modify the sign bit of a floatingpoint
value as an integer. This also works if none of the targets integer
types is big enough to hold all bits of the floatingpoint value.
- Legalize FABS(x) as FCOPYSIGN(x, 0.0) if FCOPYSIGN is available,
otherwise perform bit manipulation on the sign bit. The previous code
used "x >u 0 ? x : -x" which is incorrect for x being -0.0! It also
takes 34 instructions on ARM Cortex-M4. With this patch we only
require 5:
vldr d0, LCPI0_0
vmov r2, r3, d0
lsrs r2, r3, #31
bfi r1, r2, #31, #1
bx lr
(This could be further improved if the compiler would recognize that
r2, r3 is zero).
- Only lower FCOPYSIGN(x, y) = sign(x) ? -FABS(x) : FABS(x) if FABS is
available otherwise perform bit manipulation on the sign bit.
- Perform the sign(x) test by masking out the sign bit and comparing
with 0 rather than shifting the sign bit to the highest position and
testing for "<s 0". For x86 copysignl (on 80bit values) this gets us:
testl $32768, %eax
rather than:
shlq $48, %rax
sets %al
testb %al, %al
Differential Revision: http://reviews.llvm.org/D11172
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
llvm/trunk/test/CodeGen/Thumb2/float-intrinsics-double.ll
llvm/trunk/test/CodeGen/X86/pr13577.ll
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp?rev=252839&r1=252838&r2=252839&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp Wed Nov 11 19:02:47 2015
@@ -39,6 +39,10 @@ using namespace llvm;
#define DEBUG_TYPE "legalizedag"
+namespace {
+
+struct FloatSignAsInt;
+
//===----------------------------------------------------------------------===//
/// This takes an arbitrary SelectionDAG as input and
/// hacks on it until the target machine can handle it. This involves
@@ -51,7 +55,6 @@ using namespace llvm;
/// 'setcc' instruction efficiently, but does support 'brcc' instruction, this
/// will attempt merge setcc and brc instructions into brcc's.
///
-namespace {
class SelectionDAGLegalize {
const TargetMachine &TM;
const TargetLowering &TLI;
@@ -130,7 +133,11 @@ private:
SDValue ExpandSCALAR_TO_VECTOR(SDNode *Node);
void ExpandDYNAMIC_STACKALLOC(SDNode *Node,
SmallVectorImpl<SDValue> &Results);
- SDValue ExpandFCOPYSIGN(SDNode *Node);
+ void getSignAsIntValue(FloatSignAsInt &State, SDLoc DL, SDValue Value) const;
+ SDValue modifySignAsInt(const FloatSignAsInt &State, SDLoc DL,
+ SDValue NewIntValue) const;
+ SDValue ExpandFCOPYSIGN(SDNode *Node) const;
+ SDValue ExpandFABS(SDNode *Node) const;
SDValue ExpandLegalINT_TO_FP(bool isSigned, SDValue LegalOp, EVT DestVT,
SDLoc dl);
SDValue PromoteLegalINT_TO_FP(SDValue LegalOp, EVT DestVT, bool isSigned,
@@ -1585,69 +1592,143 @@ SDValue SelectionDAGLegalize::ExpandVect
false, false, false, 0);
}
-SDValue SelectionDAGLegalize::ExpandFCOPYSIGN(SDNode* Node) {
- SDLoc dl(Node);
- SDValue Tmp1 = Node->getOperand(0);
- SDValue Tmp2 = Node->getOperand(1);
+namespace {
+/// Keeps track of state when getting the sign of a floating-point value as an
+/// integer.
+struct FloatSignAsInt {
+ EVT FloatVT;
+ SDValue Chain;
+ SDValue FloatPtr;
+ SDValue IntPtr;
+ MachinePointerInfo IntPointerInfo;
+ MachinePointerInfo FloatPointerInfo;
+ SDValue IntValue;
+ APInt SignMask;
+};
+}
- // Get the sign bit of the RHS. First obtain a value that has the same
- // sign as the sign bit, i.e. negative if and only if the sign bit is 1.
- SDValue SignBit;
- EVT FloatVT = Tmp2.getValueType();
- EVT IVT = EVT::getIntegerVT(*DAG.getContext(), FloatVT.getSizeInBits());
+/// Bitcast a floating-point value to an integer value. Only bitcast the part
+/// containing the sign bit if the target has no integer value capable of
+/// holding all bits of the floating-point value.
+void SelectionDAGLegalize::getSignAsIntValue(FloatSignAsInt &State,
+ SDLoc DL, SDValue Value) const {
+ EVT FloatVT = Value.getValueType();
+ unsigned NumBits = FloatVT.getSizeInBits();
+ State.FloatVT = FloatVT;
+ EVT IVT = EVT::getIntegerVT(*DAG.getContext(), NumBits);
+ // Convert to an integer of the same size.
if (TLI.isTypeLegal(IVT)) {
- // Convert to an integer with the same sign bit.
- SignBit = DAG.getNode(ISD::BITCAST, dl, IVT, Tmp2);
+ State.IntValue = DAG.getNode(ISD::BITCAST, DL, IVT, Value);
+ State.SignMask = APInt::getSignBit(NumBits);
+ return;
+ }
+
+ auto &DataLayout = DAG.getDataLayout();
+ // Store the float to memory, then load the sign part out as an integer.
+ MVT LoadTy = TLI.getRegisterType(*DAG.getContext(), MVT::i8);
+ // First create a temporary that is aligned for both the load and store.
+ SDValue StackPtr = DAG.CreateStackTemporary(FloatVT, LoadTy);
+ int FI = cast<FrameIndexSDNode>(StackPtr.getNode())->getIndex();
+ // Then store the float to it.
+ State.FloatPtr = StackPtr;
+ MachineFunction &MF = DAG.getMachineFunction();
+ State.FloatPointerInfo = MachinePointerInfo::getFixedStack(MF, FI);
+ State.Chain = DAG.getStore(DAG.getEntryNode(), DL, Value, State.FloatPtr,
+ State.FloatPointerInfo, false, false, 0);
+
+ SDValue IntPtr;
+ if (DataLayout.isBigEndian()) {
+ assert(FloatVT.isByteSized() && "Unsupported floating point type!");
+ // Load out a legal integer with the same sign bit as the float.
+ IntPtr = StackPtr;
+ State.IntPointerInfo = State.FloatPointerInfo;
} else {
- auto &DL = DAG.getDataLayout();
- // Store the float to memory, then load the sign part out as an integer.
- MVT LoadTy = TLI.getPointerTy(DL);
- // First create a temporary that is aligned for both the load and store.
- SDValue StackPtr = DAG.CreateStackTemporary(FloatVT, LoadTy);
- // Then store the float to it.
- SDValue Ch =
- DAG.getStore(DAG.getEntryNode(), dl, Tmp2, StackPtr, MachinePointerInfo(),
- false, false, 0);
- if (DL.isBigEndian()) {
- assert(FloatVT.isByteSized() && "Unsupported floating point type!");
- // Load out a legal integer with the same sign bit as the float.
- SignBit = DAG.getLoad(LoadTy, dl, Ch, StackPtr, MachinePointerInfo(),
- false, false, false, 0);
- } else { // Little endian
- SDValue LoadPtr = StackPtr;
- // The float may be wider than the integer we are going to load. Advance
- // the pointer so that the loaded integer will contain the sign bit.
- unsigned Strides = (FloatVT.getSizeInBits()-1)/LoadTy.getSizeInBits();
- unsigned ByteOffset = (Strides * LoadTy.getSizeInBits()) / 8;
- LoadPtr = DAG.getNode(ISD::ADD, dl, LoadPtr.getValueType(), LoadPtr,
- DAG.getConstant(ByteOffset, dl,
- LoadPtr.getValueType()));
- // Load a legal integer containing the sign bit.
- SignBit = DAG.getLoad(LoadTy, dl, Ch, LoadPtr, MachinePointerInfo(),
- false, false, false, 0);
- // Move the sign bit to the top bit of the loaded integer.
- unsigned BitShift = LoadTy.getSizeInBits() -
- (FloatVT.getSizeInBits() - 8 * ByteOffset);
- assert(BitShift < LoadTy.getSizeInBits() && "Pointer advanced wrong?");
- if (BitShift)
- SignBit = DAG.getNode(
- ISD::SHL, dl, LoadTy, SignBit,
- DAG.getConstant(BitShift, dl,
- TLI.getShiftAmountTy(SignBit.getValueType(), DL)));
- }
- }
- // Now get the sign bit proper, by seeing whether the value is negative.
- SignBit = DAG.getSetCC(dl, getSetCCResultType(SignBit.getValueType()),
- SignBit,
- DAG.getConstant(0, dl, SignBit.getValueType()),
- ISD::SETLT);
- // Get the absolute value of the result.
- SDValue AbsVal = DAG.getNode(ISD::FABS, dl, Tmp1.getValueType(), Tmp1);
- // Select between the nabs and abs value based on the sign bit of
- // the input.
- return DAG.getSelect(dl, AbsVal.getValueType(), SignBit,
- DAG.getNode(ISD::FNEG, dl, AbsVal.getValueType(), AbsVal),
- AbsVal);
+ // Advance the pointer so that the loaded byte will contain the sign bit.
+ unsigned ByteOffset = (FloatVT.getSizeInBits() / 8) - 1;
+ IntPtr = DAG.getNode(ISD::ADD, DL, StackPtr.getValueType(), StackPtr,
+ DAG.getConstant(ByteOffset, DL, StackPtr.getValueType()));
+ State.IntPointerInfo = MachinePointerInfo::getFixedStack(MF, FI,
+ ByteOffset);
+ }
+
+ State.IntPtr = IntPtr;
+ State.IntValue = DAG.getExtLoad(ISD::EXTLOAD, DL, LoadTy, State.Chain,
+ IntPtr, State.IntPointerInfo, MVT::i8,
+ false, false, false, 0);
+ State.SignMask = APInt::getOneBitSet(LoadTy.getSizeInBits(), 7);
+}
+
+/// Replace the integer value produced by getSignAsIntValue() with a new value
+/// and cast the result back to a floating-point type.
+SDValue SelectionDAGLegalize::modifySignAsInt(const FloatSignAsInt &State,
+ SDLoc DL, SDValue NewIntValue) const {
+ if (!State.Chain)
+ return DAG.getNode(ISD::BITCAST, DL, State.FloatVT, NewIntValue);
+
+ // Override the part containing the sign bit in the value stored on the stack.
+ SDValue Chain = DAG.getTruncStore(State.Chain, DL, NewIntValue, State.IntPtr,
+ State.IntPointerInfo, MVT::i8, false, false,
+ 0);
+ return DAG.getLoad(State.FloatVT, DL, Chain, State.FloatPtr,
+ State.FloatPointerInfo, false, false, false, 0);
+}
+
+SDValue SelectionDAGLegalize::ExpandFCOPYSIGN(SDNode *Node) const {
+ SDLoc DL(Node);
+ SDValue Mag = Node->getOperand(0);
+ SDValue Sign = Node->getOperand(1);
+
+ // Get sign bit into an integer value.
+ FloatSignAsInt SignAsInt;
+ getSignAsIntValue(SignAsInt, DL, Sign);
+
+ EVT IntVT = SignAsInt.IntValue.getValueType();
+ SDValue SignMask = DAG.getConstant(SignAsInt.SignMask, DL, IntVT);
+ SDValue SignBit = DAG.getNode(ISD::AND, DL, IntVT, SignAsInt.IntValue,
+ SignMask);
+
+ // If FABS is legal transform FCOPYSIGN(x, y) => sign(x) ? -FABS(x) : FABS(X)
+ EVT FloatVT = Mag.getValueType();
+ if (TLI.isOperationLegalOrCustom(ISD::FABS, FloatVT) &&
+ TLI.isOperationLegalOrCustom(ISD::FNEG, FloatVT)) {
+ SDValue AbsValue = DAG.getNode(ISD::FABS, DL, FloatVT, Mag);
+ SDValue NegValue = DAG.getNode(ISD::FNEG, DL, FloatVT, AbsValue);
+ SDValue Cond = DAG.getSetCC(DL, getSetCCResultType(IntVT), SignBit,
+ DAG.getConstant(0, DL, IntVT), ISD::SETNE);
+ return DAG.getSelect(DL, FloatVT, Cond, NegValue, AbsValue);
+ }
+
+ // Transform values to integer, copy the sign bit and transform back.
+ FloatSignAsInt MagAsInt;
+ getSignAsIntValue(MagAsInt, DL, Mag);
+ assert(SignAsInt.SignMask == MagAsInt.SignMask);
+ SDValue ClearSignMask = DAG.getConstant(~SignAsInt.SignMask, DL, IntVT);
+ SDValue ClearedSign = DAG.getNode(ISD::AND, DL, IntVT, MagAsInt.IntValue,
+ ClearSignMask);
+ SDValue CopiedSign = DAG.getNode(ISD::OR, DL, IntVT, ClearedSign, SignBit);
+
+ return modifySignAsInt(MagAsInt, DL, CopiedSign);
+}
+
+SDValue SelectionDAGLegalize::ExpandFABS(SDNode *Node) const {
+ SDLoc DL(Node);
+ SDValue Value = Node->getOperand(0);
+
+ // Transform FABS(x) => FCOPYSIGN(x, 0.0) if FCOPYSIGN is legal.
+ EVT FloatVT = Value.getValueType();
+ if (TLI.isOperationLegalOrCustom(ISD::FCOPYSIGN, FloatVT)) {
+ SDValue Zero = DAG.getConstantFP(0.0, DL, FloatVT);
+ return DAG.getNode(ISD::FCOPYSIGN, DL, FloatVT, Value, Zero);
+ }
+
+ // Transform value to integer, clear the sign bit and transform back.
+ FloatSignAsInt ValueAsInt;
+ getSignAsIntValue(ValueAsInt, DL, Value);
+ EVT IntVT = ValueAsInt.IntValue.getValueType();
+ SDValue ClearSignMask = DAG.getConstant(~ValueAsInt.SignMask, DL, IntVT);
+ SDValue ClearedSign = DAG.getNode(ISD::AND, DL, IntVT, ValueAsInt.IntValue,
+ ClearSignMask);
+ return modifySignAsInt(ValueAsInt, DL, ClearedSign);
}
void SelectionDAGLegalize::ExpandDYNAMIC_STACKALLOC(SDNode* Node,
@@ -3196,18 +3277,9 @@ bool SelectionDAGLegalize::ExpandNode(SD
Node->getOperand(0));
Results.push_back(Tmp1);
break;
- case ISD::FABS: {
- // Expand Y = FABS(X) -> Y = (X >u 0.0) ? X : fneg(X).
- EVT VT = Node->getValueType(0);
- Tmp1 = Node->getOperand(0);
- Tmp2 = DAG.getConstantFP(0.0, dl, VT);
- Tmp2 = DAG.getSetCC(dl, getSetCCResultType(Tmp1.getValueType()),
- Tmp1, Tmp2, ISD::SETUGT);
- Tmp3 = DAG.getNode(ISD::FNEG, dl, VT, Tmp1);
- Tmp1 = DAG.getSelect(dl, VT, Tmp2, Tmp1, Tmp3);
- Results.push_back(Tmp1);
+ case ISD::FABS:
+ Results.push_back(ExpandFABS(Node));
break;
- }
case ISD::SMIN:
case ISD::SMAX:
case ISD::UMIN:
Modified: llvm/trunk/test/CodeGen/Thumb2/float-intrinsics-double.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Thumb2/float-intrinsics-double.ll?rev=252839&r1=252838&r2=252839&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/Thumb2/float-intrinsics-double.ll (original)
+++ llvm/trunk/test/CodeGen/Thumb2/float-intrinsics-double.ll Wed Nov 11 19:02:47 2015
@@ -109,8 +109,12 @@ declare double @llvm.fabs.f64(double
define double @abs_d(double %a) {
; CHECK-LABEL: abs_d:
; NONE: bic r1, r1, #-2147483648
-; SP: bl __aeabi_dsub
-; SP: bl __aeabi_dcmple
+; SP: vldr d1, .LCPI{{.*}}
+; SP: vmov r0, r1, d0
+; SP: vmov r2, r3, d1
+; SP: lsrs r2, r3, #31
+; SP: bfi r1, r2, #31, #1
+; SP: vmov d0, r0, r1
; DP: vabs.f64 d0, d0
%1 = call double @llvm.fabs.f64(double %a)
ret double %1
Modified: llvm/trunk/test/CodeGen/X86/pr13577.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr13577.ll?rev=252839&r1=252838&r2=252839&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr13577.ll (original)
+++ llvm/trunk/test/CodeGen/X86/pr13577.ll Wed Nov 11 19:02:47 2015
@@ -6,10 +6,7 @@
; CHECK-NEXT: .long 2139095040
; CHECK-LABEL: foo:
-; CHECK: movq {{.*}}, %rax
-; CHECK: shlq $48, %rax
-; CHECK: sets %al
-; CHECK: testb %al, %al
+; CHECK: testb $-128, -15(%rsp)
; CHECK: flds LCPI0_0(%rip)
; CHECK: flds LCPI0_1(%rip)
; CHECK: fcmovne %st(1), %st(0)
More information about the llvm-commits
mailing list