Rules for tan (rust-lang#793)

Author: sriharikrishna

enzyme/Enzyme/InstructionDerivatives.td

@@ -107,6 +107,9 @@ def : CallPattern<(Op $x),
                   ["exp10"],
                   [(FMul (FMul (DiffeRet<"">), (Call<(SameFunc), [ReadNone,NoUnwind]> $x) ), (ConstantFP<"2.30258509299404568401799145468"> $x))]
                   >;
+def : CallPattern<(Op $x),
+                  ["tan", "tanf", "tanl"],
+                  [(FMul (DiffeRet<"">), (FAdd (ConstantFP<"1.0"> $x), (FMul(Call<(SameFunc), [ReadNone,NoUnwind]> $x):$c, $c)))]>;
 
 // TODO replace with intrinsic call to exp
 def : CallPattern<(Op $x),

enzyme/test/Enzyme/ForwardMode/tan.ll

@@ -0,0 +1,29 @@
+; 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 @tan(double %x)
+  ret double %0
+}
+
+define double @test_derivative(double %x) {
+entry:
+  %0 = tail call double (double (double)*, ...) @__enzyme_fwddiff(double (double)* nonnull @tester, double %x, double 1.0)
+  ret double %0
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare double @tan(double)
+
+; Function Attrs: nounwind
+declare double @__enzyme_fwddiff(double (double)*, ...)
+
+; CHECK: define internal double @fwddiffetester(double %x, double %"x'")
+; CHECK-NEXT: entry:
+; CHECK-NEXT:   %0 = call fast double @tan(double %x)
+; CHECK-NEXT:   %1 = fmul fast double %0, %0
+; CHECK-NEXT:   %2 = fadd fast double 1.000000e+00, %1
+; CHECK-NEXT:   %3 = fmul fast double %"x'", %2
+; CHECK-NEXT:   ret double %3
+; CHECK-NEXT: }

enzyme/test/Enzyme/ReverseMode/tan.ll

@@ -0,0 +1,30 @@
+; 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 @tan(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 @tan(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 = call fast double @tan(double %x) 
+; CHECK-NEXT:   %1 = fmul fast double %0, %0
+; CHECK-NEXT:   %2 = fadd fast double 1.000000e+00, %1
+; CHECK-NEXT:   %3 = fmul fast double %differeturn, %2
+; CHECK-NEXT:   %4 = insertvalue { double } undef, double %3, 0
+; CHECK-NEXT:   ret { double } %4
+; CHECK-NEXT: }