Add sinc normalized (rust-lang#834)

Author: wsmoses

enzyme/Enzyme/InstructionDerivatives.td

@@ -143,6 +143,12 @@ def : CallPattern<(Op $x),
                   [(FMul (Intrinsic<"exp", [(TypeOf<""> $x)]> $x), (DiffeRet<"">))]
                   >;
 
+// Unnormalized sinc(x) = sin(x)/x
 def : CallPattern<(Op $x),
                   ["sinc", "sincf", "sincl"],
                   [(FMul (DiffeRet<"">), (FDiv (FSub (Intrinsic<"cos", [(TypeOf<""> $x)]> $x), (Call<(SameFunc), [ReadNone,NoUnwind]> $x)), $x))]>;
+
+// Normalized sinc(x) = sin(pi x)/(pi x)
+def : CallPattern<(Op $x),
+                  ["sincn", "sincnf", "sincnl"],
+                  [(FMul (DiffeRet<"">), (FDiv (FSub (Intrinsic<"cos", [(TypeOf<""> $x)]> (FMul (ConstantFP<"3.1415926535897962684626433"> $x), $x)), (Call<(SameFunc), [ReadNone,NoUnwind]> $x)), $x))]>;

enzyme/Enzyme/TypeAnalysis/TypeAnalysis.cpp

@@ -74,6 +74,7 @@ llvm::cl::opt<bool> EnzymeStrictAliasing(
 
 const std::map<std::string, llvm::Intrinsic::ID> LIBM_FUNCTIONS = {
     {"sinc", Intrinsic::not_intrinsic},
+    {"sincn", Intrinsic::not_intrinsic},
     {"cos", Intrinsic::cos},
     {"sin", Intrinsic::sin},
     {"tan", Intrinsic::not_intrinsic},

enzyme/test/Enzyme/ReverseMode/sincn.ll

@@ -0,0 +1,32 @@
+; RUN: %opt < %s %loadEnzyme -enzyme -enzyme-preopt=false -mem2reg -instsimplify -simplifycfg -S | FileCheck %s
+
+; Function Attrs: nounwind readnone uwtable
+define double @tester(double %x) {
+entry:
+  %0 = tail call fast double @sincn(double %x)
+  ret double %0
+}
+
+define double @test_derivative(double %x) {
+entry:
+  %0 = tail call double (double (double)*, ...) @__enzyme_autodiff(double (double)* nonnull @tester, double %x)
+  ret double %0
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare double @sincn(double)
+
+; Function Attrs: nounwind
+declare double @__enzyme_autodiff(double (double)*, ...)
+
+; CHECK: define internal { double } @diffetester(double %x, double %differeturn)
+; CHECK-NEXT: entry:
+; CHECK-NEXT:   %0 = fmul fast double 0x400921FB54442D1F, %x
+; CHECK-NEXT:   %[[i0:.+]] = call fast double @llvm.cos.f64(double %0)
+; CHECK-NEXT:   %[[i1:.+]] = call fast double @sincn(double %x)
+; CHECK-NEXT:   %[[i2:.+]] = fsub fast double %[[i0]], %[[i1]]
+; CHECK-NEXT:   %[[i3:.+]] = fdiv fast double %[[i2]], %x
+; CHECK-NEXT:   %[[i4:.+]] = fmul fast double %differeturn, %[[i3]]
+; CHECK-NEXT:   %[[i5:.+]] = insertvalue { double } undef, double %[[i4]], 0
+; CHECK-NEXT:   ret { double } %[[i5]]
+; CHECK-NEXT: }