[llvm-commits] [llvm] r147593 - /llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
Bill Wendling
isanbard at gmail.com
Wed Jan 4 18:13:20 PST 2012
Author: void
Date: Wed Jan 4 20:13:20 2012
New Revision: 147593
URL: http://llvm.org/viewvc/llvm-project?rev=147593&view=rev
Log:
Replace the uint64_t -> double convertion algorithm with one that's more efficient.
This small bit of ASM code is sufficient to do what the old algorithm did:
movq %rax, %xmm0
punpckldq (c0), %xmm0 // c0: (uint4){ 0x43300000U, 0x45300000U, 0U, 0U }
subpd (c1), %xmm0 // c1: (double2){ 0x1.0p52, 0x1.0p52 * 0x1.0p32 }
#ifdef __SSE3__
haddpd %xmm0, %xmm0
#else
pshufd $0x4e, %xmm0, %xmm1
addpd %xmm1, %xmm0
#endif
It's arguably faster. One caveat, the 'haddpd' instruction isn't very fast on
all processors.
<rdar://problem/7719814>
Modified:
llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=147593&r1=147592&r2=147593&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Wed Jan 4 20:13:20 2012
@@ -256,7 +256,7 @@
if (Subtarget->is64Bit()) {
setOperationAction(ISD::UINT_TO_FP , MVT::i32 , Promote);
- setOperationAction(ISD::UINT_TO_FP , MVT::i64 , Expand);
+ setOperationAction(ISD::UINT_TO_FP , MVT::i64 , Custom);
} else if (!TM.Options.UseSoftFloat) {
// We have an algorithm for SSE2->double, and we turn this into a
// 64-bit FILD followed by conditional FADD for other targets.
@@ -7581,38 +7581,17 @@
// LowerUINT_TO_FP_i64 - 64-bit unsigned integer to double expansion.
SDValue X86TargetLowering::LowerUINT_TO_FP_i64(SDValue Op,
SelectionDAG &DAG) const {
- // This algorithm is not obvious. Here it is in C code, more or less:
+ // This algorithm is not obvious. Here it is what we're trying to output:
/*
- double uint64_to_double( uint32_t hi, uint32_t lo ) {
- static const __m128i exp = { 0x4330000045300000ULL, 0 };
- static const __m128d bias = { 0x1.0p84, 0x1.0p52 };
-
- // Copy ints to xmm registers.
- __m128i xh = _mm_cvtsi32_si128( hi );
- __m128i xl = _mm_cvtsi32_si128( lo );
-
- // Combine into low half of a single xmm register.
- __m128i x = _mm_unpacklo_epi32( xh, xl );
- __m128d d;
- double sd;
-
- // Merge in appropriate exponents to give the integer bits the right
- // magnitude.
- x = _mm_unpacklo_epi32( x, exp );
-
- // Subtract away the biases to deal with the IEEE-754 double precision
- // implicit 1.
- d = _mm_sub_pd( (__m128d) x, bias );
-
- // All conversions up to here are exact. The correctly rounded result is
- // calculated using the current rounding mode using the following
- // horizontal add.
- d = _mm_add_sd( d, _mm_unpackhi_pd( d, d ) );
- _mm_store_sd( &sd, d ); // Because we are returning doubles in XMM, this
- // store doesn't really need to be here (except
- // maybe to zero the other double)
- return sd;
- }
+ movq %rax, %xmm0
+ punpckldq (c0), %xmm0 // c0: (uint4){ 0x43300000U, 0x45300000U, 0U, 0U }
+ subpd (c1), %xmm0 // c1: (double2){ 0x1.0p52, 0x1.0p52 * 0x1.0p32 }
+ #ifdef __SSE3__
+ haddpd %xmm0, %xmm0
+ #else
+ pshufd $0x4e, %xmm0, %xmm1
+ addpd %xmm1, %xmm0
+ #endif
*/
DebugLoc dl = Op.getDebugLoc();
@@ -7620,8 +7599,8 @@
// Build some magic constants.
SmallVector<Constant*,4> CV0;
- CV0.push_back(ConstantInt::get(*Context, APInt(32, 0x45300000)));
CV0.push_back(ConstantInt::get(*Context, APInt(32, 0x43300000)));
+ CV0.push_back(ConstantInt::get(*Context, APInt(32, 0x45300000)));
CV0.push_back(ConstantInt::get(*Context, APInt(32, 0)));
CV0.push_back(ConstantInt::get(*Context, APInt(32, 0)));
Constant *C0 = ConstantVector::get(CV0);
@@ -7629,37 +7608,42 @@
SmallVector<Constant*,2> CV1;
CV1.push_back(
- ConstantFP::get(*Context, APFloat(APInt(64, 0x4530000000000000ULL))));
- CV1.push_back(
ConstantFP::get(*Context, APFloat(APInt(64, 0x4330000000000000ULL))));
+ CV1.push_back(
+ ConstantFP::get(*Context, APFloat(APInt(64, 0x4530000000000000ULL))));
Constant *C1 = ConstantVector::get(CV1);
SDValue CPIdx1 = DAG.getConstantPool(C1, getPointerTy(), 16);
- SDValue XR1 = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, MVT::v4i32,
- DAG.getNode(ISD::EXTRACT_ELEMENT, dl, MVT::i32,
- Op.getOperand(0),
- DAG.getIntPtrConstant(1)));
- SDValue XR2 = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, MVT::v4i32,
- DAG.getNode(ISD::EXTRACT_ELEMENT, dl, MVT::i32,
- Op.getOperand(0),
- DAG.getIntPtrConstant(0)));
- SDValue Unpck1 = getUnpackl(DAG, dl, MVT::v4i32, XR1, XR2);
+ // Load the 64-bit value into an XMM register.
+ SDValue XR1 = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, MVT::v2i64,
+ Op.getOperand(0));
SDValue CLod0 = DAG.getLoad(MVT::v4i32, dl, DAG.getEntryNode(), CPIdx0,
MachinePointerInfo::getConstantPool(),
false, false, false, 16);
- SDValue Unpck2 = getUnpackl(DAG, dl, MVT::v4i32, Unpck1, CLod0);
- SDValue XR2F = DAG.getNode(ISD::BITCAST, dl, MVT::v2f64, Unpck2);
+ SDValue Unpck1 = getUnpackl(DAG, dl, MVT::v4i32,
+ DAG.getNode(ISD::BITCAST, dl, MVT::v4i32, XR1),
+ CLod0);
+
SDValue CLod1 = DAG.getLoad(MVT::v2f64, dl, CLod0.getValue(1), CPIdx1,
MachinePointerInfo::getConstantPool(),
false, false, false, 16);
+ SDValue XR2F = DAG.getNode(ISD::BITCAST, dl, MVT::v2f64, Unpck1);
SDValue Sub = DAG.getNode(ISD::FSUB, dl, MVT::v2f64, XR2F, CLod1);
+ SDValue Result;
- // Add the halves; easiest way is to swap them into another reg first.
- int ShufMask[2] = { 1, -1 };
- SDValue Shuf = DAG.getVectorShuffle(MVT::v2f64, dl, Sub,
- DAG.getUNDEF(MVT::v2f64), ShufMask);
- SDValue Add = DAG.getNode(ISD::FADD, dl, MVT::v2f64, Shuf, Sub);
- return DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, MVT::f64, Add,
+ if (Subtarget->hasSSE3()) {
+ // FIXME: The 'haddpd' instruction may be slower than 'movhlps + addsd'.
+ Result = DAG.getNode(X86ISD::FHADD, dl, MVT::v2f64, Sub, Sub);
+ } else {
+ SDValue S2F = DAG.getNode(ISD::BITCAST, dl, MVT::v4i32, Sub);
+ SDValue Shuffle = getTargetShuffleNode(X86ISD::PSHUFD, dl, MVT::v4i32,
+ S2F, 0x4E, DAG);
+ Result = DAG.getNode(ISD::FADD, dl, MVT::v2f64,
+ DAG.getNode(ISD::BITCAST, dl, MVT::v2f64, Shuffle),
+ Sub);
+ }
+
+ return DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, MVT::f64, Result,
DAG.getIntPtrConstant(0));
}
@@ -7729,6 +7713,8 @@
return LowerUINT_TO_FP_i64(Op, DAG);
else if (SrcVT == MVT::i32 && X86ScalarSSEf64)
return LowerUINT_TO_FP_i32(Op, DAG);
+ else if (SrcVT == MVT::i64 && DstVT == MVT::f32)
+ return SDValue();
// Make a 64-bit buffer, and use it to build an FILD.
SDValue StackSlot = DAG.CreateStackTemporary(MVT::i64);
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