Add the next limited-precision expansion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55856 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 42 insertions, 3 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
index c7e2cd5..7cd2bb2 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
@@ -2798,10 +2798,49 @@ SelectionDAGLowering::visitLog2(CallInst &I) {
 void
 SelectionDAGLowering::visitLog10(CallInst &I) {
   SDValue result;
+  if (getValue(I.getOperand(1)).getValueType() == MVT::f32 &&
+      LimitFloatPrecision>0 && LimitFloatPrecision<=12) {
+    SDValue operand = getValue(I.getOperand(1));
+    SDValue operand1 = DAG.getNode(ISD::BIT_CONVERT, MVT::i32, operand);
+    SDValue t0 = DAG.getNode(ISD::SRL, MVT::i32, operand1, 
+                                       DAG.getConstant(23, MVT::i32));
+    SDValue t1 = DAG.getNode(ISD::AND, MVT::i32, t0,
+                                       DAG.getConstant(255, MVT::i32));
+    SDValue t2 = DAG.getNode(ISD::SUB, MVT::i32, t1,
+                                       DAG.getConstant(127, MVT::i32));
+    SDValue t3 = DAG.getNode(ISD::UINT_TO_FP, MVT::f32, t2);
+    SDValue t4 = DAG.getNode(ISD::FMUL, MVT::f32, t3,
+                      DAG.getConstantFP(APFloat(
+                          APInt(32, 0x3e9a209a)), MVT::f32));
+    SDValue t5 = DAG.getNode(ISD::OR, MVT::i32, operand1,
+                                       DAG.getConstant(1065353216, MVT::i32));
+    SDValue t6 = DAG.getNode(ISD::AND, MVT::i32, t5,
+                                       DAG.getConstant(1073741823, MVT::i32));
+    SDValue t7 = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t6);
+    SDValue t8 = DAG.getNode(ISD::FP_EXTEND, MVT::f64, t7);
+    SDValue t9 = DAG.getNode(ISD::FMUL, MVT::f64, t8,
+                      DAG.getConstantFP(APFloat(
+                          APInt(64, 0x3fa863e61d44a337ULL)), MVT::f64));
+    SDValue t10 = DAG.getNode(ISD::FSUB, MVT::f64, t9,
+                      DAG.getConstantFP(APFloat(
+                          APInt(64, 0x3fd443f63982ad9aULL)), MVT::f64));
+    SDValue t11 = DAG.getNode(ISD::FMUL, MVT::f64, t10, t8);
+    SDValue t12 = DAG.getNode(ISD::FADD, MVT::f64, t11,
+                      DAG.getConstantFP(APFloat(
+                          APInt(64, 0x3fed5c4641d8bd71ULL)), MVT::f64));
+    SDValue t13 = DAG.getNode(ISD::FMUL, MVT::f64, t12, t8);
+    SDValue t14 = DAG.getNode(ISD::FSUB, MVT::f64, t13,
+                      DAG.getConstantFP(APFloat(
+                          APInt(64, 0x3fe4bef863538c6fULL)), MVT::f64));
+    SDValue t15 = DAG.getNode(ISD::FP_ROUND, MVT::f32, t14, 
+                          DAG.getConstant(0, MVT::i32));
+    result = DAG.getNode(ISD::FADD, MVT::f32, t4, t15);
+  } else {
   // No special expansion.
-  result = DAG.getNode(ISD::FLOG10,
-                       getValue(I.getOperand(1)).getValueType(),
-                       getValue(I.getOperand(1)));
+    result = DAG.getNode(ISD::FLOG10,
+                         getValue(I.getOperand(1)).getValueType(),
+                         getValue(I.getOperand(1)));
+  }
   setValue(&I, result);
 }