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[X86] Teach FCOPYSIGN lowering to recognize constant magnitudes.

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For code like:
    float foo(float x) { return copysign(1.0, x); }
We used to generate:
    andps  <-0.000000e+00,0,0,0>, %xmm0
    movss  <1.000000e+00>, %xmm1
    andps  <nan>, %xmm1
    orps   %xmm0, %xmm1
Basically doing an abs(1.0f) in the two middle instructions.

We now generate:
    andps  <-0.000000e+00,0,0,0>, %xmm0
    orps   <1.000000e+00,0,0,0>, %xmm0

Builds on cleanups r223415, r223542.
rdar://19049548
Differential Revision: http://reviews.llvm.org/D6555


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225357 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ahmed Bougacha 2015-01-07 17:33:03 +00:00
parent 1763c0ad7f
commit d412c608fc
3 changed files with 124 additions and 20 deletions
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25
lib/Target/X86/X86ISelLowering.cpp
View File

@ -14530,14 +14530,27 @@ static SDValue LowerFCOPYSIGN(SDValue Op, SelectionDAG &DAG) {
SDValue SignBit = DAG.getNode(X86ISD::FAND, dl, SrcVT, Op1, Mask1);
// Next, clear the sign bit from the first operand (magnitude).
CV[0] = ConstantFP::get(
*Context, APFloat(Sem, APInt::getLowBitsSet(SizeInBits, SizeInBits - 1)));
// If it's a constant, we can clear it here.
if (ConstantFPSDNode *Op0CN = dyn_cast<ConstantFPSDNode>(Op0)) {
APFloat APF = Op0CN->getValueAPF();
// If the magnitude is a positive zero, the sign bit alone is enough.
if (APF.isPosZero())
return SignBit;
APF.clearSign();
CV[0] = ConstantFP::get(*Context, APF);
} else {
CV[0] = ConstantFP::get(
*Context,
APFloat(Sem, APInt::getLowBitsSet(SizeInBits, SizeInBits - 1)));
}
C = ConstantVector::get(CV);
CPIdx = DAG.getConstantPool(C, TLI.getPointerTy(), 16);
SDValue Mask2 = DAG.getLoad(VT, dl, DAG.getEntryNode(), CPIdx,
MachinePointerInfo::getConstantPool(),
false, false, false, 16);
SDValue Val = DAG.getNode(X86ISD::FAND, dl, VT, Op0, Mask2);
SDValue Val = DAG.getLoad(VT, dl, DAG.getEntryNode(), CPIdx,
MachinePointerInfo::getConstantPool(),
false, false, false, 16);
// If the magnitude operand wasn't a constant, we need to AND out the sign.
if (!isa<ConstantFPSDNode>(Op0))
Val = DAG.getNode(X86ISD::FAND, dl, VT, Op0, Val);
// OR the magnitude value with the sign bit.
return DAG.getNode(X86ISD::FOR, dl, VT, Val, SignBit);

105
test/CodeGen/X86/copysign-constant-magnitude.ll Normal file
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@ -0,0 +1,105 @@
; RUN: llc < %s | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.10.0"
define void @test_copysign_const_magnitude_d(double %X) {
; CHECK: [[SIGNMASK:L.+]]:
; CHECK-NEXT: .quad -9223372036854775808 ## double -0.000000e+00
; CHECK-NEXT: .quad 0 ## double 0.000000e+00
; CHECK: [[ZERO:L.+]]:
; CHECK-NEXT: .space 16
; CHECK: [[ONE:L.+]]:
; CHECK-NEXT: .quad 4607182418800017408 ## double 1.000000e+00
; CHECK-NEXT: .quad 0 ## double 0.000000e+00
; CHECK-LABEL: test_copysign_const_magnitude_d:
; CHECK: id
%iX = call double @id_d(double %X)
; CHECK-NEXT: andpd [[SIGNMASK]](%rip), %xmm0
%d0 = call double @copysign(double 0.000000e+00, double %iX)
; CHECK-NEXT: id
%id0 = call double @id_d(double %d0)
; CHECK-NEXT: andpd [[SIGNMASK]](%rip), %xmm0
; CHECK-NEXT: orpd [[ZERO]](%rip), %xmm0
%dn0 = call double @copysign(double -0.000000e+00, double %id0)
; CHECK-NEXT: id
%idn0 = call double @id_d(double %dn0)
; CHECK-NEXT: andpd [[SIGNMASK]](%rip), %xmm0
; CHECK-NEXT: orpd [[ONE]](%rip), %xmm0
%d1 = call double @copysign(double 1.000000e+00, double %idn0)
; CHECK-NEXT: id
%id1 = call double @id_d(double %d1)
; CHECK-NEXT: andpd [[SIGNMASK]](%rip), %xmm0
; CHECK-NEXT: orpd [[ONE]](%rip), %xmm0
%dn1 = call double @copysign(double -1.000000e+00, double %id1)
; CHECK-NEXT: id
%idn1 = call double @id_d(double %dn1)
; CHECK: retq
ret void
}
define void @test_copysign_const_magnitude_f(float %X) {
; CHECK: [[SIGNMASK:L.+]]:
; CHECK-NEXT: .long 2147483648 ## float -0.000000e+00
; CHECK-NEXT: .long 0 ## float 0.000000e+00
; CHECK-NEXT: .long 0 ## float 0.000000e+00
; CHECK-NEXT: .long 0 ## float 0.000000e+00
; CHECK: [[ZERO:L.+]]:
; CHECK-NEXT: .space 16
; CHECK: [[ONE:L.+]]:
; CHECK-NEXT: .long 1065353216 ## float 1.000000e+00
; CHECK-NEXT: .long 0 ## float 0.000000e+00
; CHECK-NEXT: .long 0 ## float 0.000000e+00
; CHECK-NEXT: .long 0 ## float 0.000000e+00
; CHECK-LABEL: test_copysign_const_magnitude_f:
; CHECK: id
%iX = call float @id_f(float %X)
; CHECK-NEXT: andps [[SIGNMASK]](%rip), %xmm0
%d0 = call float @copysignf(float 0.000000e+00, float %iX)
; CHECK-NEXT: id
%id0 = call float @id_f(float %d0)
; CHECK-NEXT: andps [[SIGNMASK]](%rip), %xmm0
; CHECK-NEXT: orps [[ZERO]](%rip), %xmm0
%dn0 = call float @copysignf(float -0.000000e+00, float %id0)
; CHECK-NEXT: id
%idn0 = call float @id_f(float %dn0)
; CHECK-NEXT: andps [[SIGNMASK]](%rip), %xmm0
; CHECK-NEXT: orps [[ONE]](%rip), %xmm0
%d1 = call float @copysignf(float 1.000000e+00, float %idn0)
; CHECK-NEXT: id
%id1 = call float @id_f(float %d1)
; CHECK-NEXT: andps [[SIGNMASK]](%rip), %xmm0
; CHECK-NEXT: orps [[ONE]](%rip), %xmm0
%dn1 = call float @copysignf(float -1.000000e+00, float %id1)
; CHECK-NEXT: id
%idn1 = call float @id_f(float %dn1)
; CHECK: retq
ret void
}
declare double @copysign(double, double) nounwind readnone
declare float @copysignf(float, float) nounwind readnone
; Dummy identity functions, so we always have xmm0, and prevent optimizations.
declare double @id_d(double)
declare float @id_f(float)

14
test/CodeGen/X86/copysign-zero.ll
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@ -1,14 +0,0 @@
; RUN: llc < %s | not grep orpd
; RUN: llc < %s | grep andpd | count 1
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-apple-darwin8"
define double @test(double %X) nounwind {
entry:
%tmp2 = tail call double @copysign( double 0.000000e+00, double %X ) nounwind readnone ; <double> [#uses=1]
ret double %tmp2
}
declare double @copysign(double, double) nounwind readnone