constant fold bits_convert in getNode and in the dag combiner for fp<->int

conversions.  This allows V8 to compiles this:

void %test() {
        call float %test2( float 1.000000e+00, float 2.000000e+00, double 3.000000e+00, double* null )
        ret void
}

into:

test:
        save -96, %o6, %o6
        sethi 0, %o3
        sethi 1049088, %o2
        sethi 1048576, %o1
        sethi 1040384, %o0
        or %g0, %o3, %o4
        call test2
        nop
        restore %g0, %g0, %g0
        retl
        nop

instead of:

test:
        save -112, %o6, %o6
        sethi 0, %o4
        sethi 1049088, %l0
        st %o4, [%i6+-12]
        st %l0, [%i6+-16]
        ld [%i6+-12], %o3
        ld [%i6+-16], %o2
        sethi 1048576, %o1
        sethi 1040384, %o0
        call test2
        nop
        restore %g0, %g0, %g0
        retl
        nop

llvm-svn: 24980

1 files changed, 22 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index ec75dfee32a..76d983f57e8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -828,6 +828,7 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT) {
 
 SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
                                 SDOperand Operand) {
+  // Constant fold unary operations with an integer constant operand.
   if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Operand.Val)) {
     uint64_t Val = C->getValue();
     switch (Opcode) {
@@ -838,13 +839,25 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
     case ISD::TRUNCATE:    return getConstant(Val, VT);
     case ISD::SINT_TO_FP:  return getConstantFP(C->getSignExtended(), VT);
     case ISD::UINT_TO_FP:  return getConstantFP(C->getValue(), VT);
+    case ISD::BIT_CONVERT:
+      if (VT == MVT::f32) {
+        assert(C->getValueType(0) == MVT::i32 && "Invalid bit_convert!");
+        return getConstantFP(BitsToFloat(Val), VT);
+      } else if (VT == MVT::f64) {
+        assert(C->getValueType(0) == MVT::i64 && "Invalid bit_convert!");
+        return getConstantFP(BitsToDouble(Val), VT);
+      }
+      break;
     }
   }
 
+  // Constant fold unary operations with an floating point constant operand.
   if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Operand.Val))
     switch (Opcode) {
     case ISD::FNEG:
       return getConstantFP(-C->getValue(), VT);
+    case ISD::FABS:
+      return getConstantFP(fabs(C->getValue()), VT);
     case ISD::FP_ROUND:
     case ISD::FP_EXTEND:
       return getConstantFP(C->getValue(), VT);
@@ -852,6 +865,15 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
       return getConstant((int64_t)C->getValue(), VT);
     case ISD::FP_TO_UINT:
       return getConstant((uint64_t)C->getValue(), VT);
+    case ISD::BIT_CONVERT:
+      if (VT == MVT::i32) {
+        assert(C->getValueType(0) == MVT::f32 && "Invalid bit_convert!");
+        return getConstant(FloatToBits(C->getValue()), VT);
+      } else if (VT == MVT::i64) {
+        assert(C->getValueType(0) == MVT::f64 && "Invalid bit_convert!");
+        return getConstant(DoubleToBits(C->getValue()), VT);
+      }
+      break;
     }
 
   unsigned OpOpcode = Operand.Val->getOpcode();