commit e60415a0db2b1696c016ad21821cc2704ee18811
author Evandro Menezes <e.menezes@samsung.com> Wed Oct 09 19:58:01 2019 +0000
committer Evandro Menezes <e.menezes@samsung.com> Wed Oct 09 19:58:01 2019 +0000
tree 05680cdc96773d35d6f85c813ef3ae18195505a1
parent 2e6f6b4dadbf2af58646bbddec45bd3233fe3d19

[Support] Add mathematical constants

Add own version of the mathematical constants from the upcoming C++20 `std::numbers`.

Differential revision: https://reviews.llvm.org/D68257

llvm-svn: 374207

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 5380630..3c36cc6 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4974,12 +4974,11 @@
     // Put the exponent in the right bit position for later addition to the
     // final result:
     //
-    //   #define LOG2OFe 1.4426950f
-    //   t0 = Op * LOG2OFe
+    // t0 = Op * log2(e)
 
     // TODO: What fast-math-flags should be set here?
     SDValue t0 = DAG.getNode(ISD::FMUL, dl, MVT::f32, Op,
-                             getF32Constant(DAG, 0x3fb8aa3b, dl));
+                             DAG.getConstantFP(numbers::log2ef, dl, MVT::f32));
     return getLimitedPrecisionExp2(t0, dl, DAG);
   }
 
@@ -4997,10 +4996,11 @@
       LimitFloatPrecision > 0 && LimitFloatPrecision <= 18) {
     SDValue Op1 = DAG.getNode(ISD::BITCAST, dl, MVT::i32, Op);
 
-    // Scale the exponent by log(2) [0.69314718f].
+    // Scale the exponent by log(2).
     SDValue Exp = GetExponent(DAG, Op1, TLI, dl);
-    SDValue LogOfExponent = DAG.getNode(ISD::FMUL, dl, MVT::f32, Exp,
-                                        getF32Constant(DAG, 0x3f317218, dl));
+    SDValue LogOfExponent =
+        DAG.getNode(ISD::FMUL, dl, MVT::f32, Exp,
+                    DAG.getConstantFP(numbers::ln2f, dl, MVT::f32));
 
     // Get the significand and build it into a floating-point number with
     // exponent of 1.

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 1fb4f28..461a5e2 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -48,7 +48,6 @@
                          cl::desc("Enable unsafe double to float "
                                   "shrinking for math lib calls"));
 
-
 //===----------------------------------------------------------------------===//
 // Helper Functions
 //===----------------------------------------------------------------------===//
@@ -1941,9 +1940,8 @@
            ArgID == Intrinsic::exp || ArgID == Intrinsic::exp2) {
     Constant *Eul;
     if (ArgLb == ExpLb || ArgID == Intrinsic::exp)
-      // FIXME: The Euler number should be M_E, but it's place of definition
-      // is not quite standard.
-      Eul = ConstantFP::get(Log->getType(), 2.7182818284590452354);
+      // FIXME: Add more precise value of e for long double.
+      Eul = ConstantFP::get(Log->getType(), numbers::e);
     else if (ArgLb == Exp2Lb || ArgID == Intrinsic::exp2)
       Eul = ConstantFP::get(Log->getType(), 2.0);
     else