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Generalize FP constant shrinking optimization to apply to any vt

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except ppc long double.  This allows us to shrink constant pool
entries for x86 long double constants, which in turn allows us to
use flds/fldl instead of fldt.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47938 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-03-05 06:48:13 +00:00
parent aa2acbbbf0
commit ec4a5672f8
2 changed files with 32 additions and 26 deletions
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49
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -44,6 +44,17 @@ static SDVTList makeVTList(const MVT::ValueType *VTs, unsigned NumVTs) {
return Res;
}
static const fltSemantics *MVTToAPFloatSemantics(MVT::ValueType VT) {
switch (VT) {
default: assert(0 && "Unknown FP format");
case MVT::f32: return &APFloat::IEEEsingle;
case MVT::f64: return &APFloat::IEEEdouble;
case MVT::f80: return &APFloat::x87DoubleExtended;
case MVT::f128: return &APFloat::IEEEquad;
case MVT::ppcf128: return &APFloat::PPCDoubleDouble;
}
}
SelectionDAG::DAGUpdateListener::~DAGUpdateListener() {}
//===----------------------------------------------------------------------===//
@ -60,28 +71,20 @@ bool ConstantFPSDNode::isExactlyValue(const APFloat& V) const {
bool ConstantFPSDNode::isValueValidForType(MVT::ValueType VT,
const APFloat& Val) {
assert(MVT::isFloatingPoint(VT) && "Can only convert between FP types");
// Anything can be extended to ppc long double.
if (VT == MVT::ppcf128)
return true;
// PPC long double cannot be shrunk to anything though.
if (&Val.getSemantics() == &APFloat::PPCDoubleDouble)
return false;
// convert modifies in place, so make a copy.
APFloat Val2 = APFloat(Val);
switch (VT) {
default:
return false; // These can't be represented as floating point!
// FIXME rounding mode needs to be more flexible
case MVT::f32:
return &Val2.getSemantics() == &APFloat::IEEEsingle ||
Val2.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven) ==
APFloat::opOK;
case MVT::f64:
return &Val2.getSemantics() == &APFloat::IEEEsingle ||
&Val2.getSemantics() == &APFloat::IEEEdouble ||
Val2.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven) ==
APFloat::opOK;
// TODO: Figure out how to test if we can use a shorter type instead!
case MVT::f80:
case MVT::f128:
case MVT::ppcf128:
return true;
}
return Val2.convert(*MVTToAPFloatSemantics(VT),
APFloat::rmNearestTiesToEven) == APFloat::opOK;
}
//===----------------------------------------------------------------------===//
@ -1786,11 +1789,7 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
case ISD::FP_EXTEND:
// This can return overflow, underflow, or inexact; we don't care.
// FIXME need to be more flexible about rounding mode.
(void) V.convert(VT==MVT::f32 ? APFloat::IEEEsingle :
VT==MVT::f64 ? APFloat::IEEEdouble :
VT==MVT::f80 ? APFloat::x87DoubleExtended :
VT==MVT::f128 ? APFloat::IEEEquad :
APFloat::Bogus,
(void)V.convert(*MVTToAPFloatSemantics(VT),
APFloat::rmNearestTiesToEven);
return getConstantFP(V, VT);
case ISD::FP_TO_SINT:

7
test/CodeGen/X86/shrink-fp-const2.ll Normal file
View File

@ -0,0 +1,7 @@
; RUN: llvm-as < %s | llc -march=x86 | grep flds
; This should be a flds, not fldt.
define x86_fp80 @test2() nounwind {
entry:
ret x86_fp80 0xK3FFFC000000000000000
}