Handle cbrt (rust-lang#235)

Author: wsmoses

enzyme/Enzyme/AdjointGenerator.h

@@ -3845,6 +3845,38 @@ class AdjointGenerator
         return;
       }
 
+      if (funcName == "cbrt") {
+        if (gutils->knownRecomputeHeuristic.find(orig) !=
+            gutils->knownRecomputeHeuristic.end()) {
+          if (!gutils->knownRecomputeHeuristic[orig]) {
+            gutils->cacheForReverse(BuilderZ, gutils->getNewFromOriginal(&call),
+                                    getIndex(orig, CacheType::Self));
+          }
+        }
+        eraseIfUnused(*orig);
+        if (Mode == DerivativeMode::ReverseModePrimal ||
+            gutils->isConstantInstruction(orig))
+          return;
+
+        IRBuilder<> Builder2(call.getParent());
+        getReverseBuilder(Builder2);
+        Value *x = lookup(gutils->getNewFromOriginal(orig->getArgOperand(0)),
+                          Builder2);
+        Value *args[] = {x};
+#if LLVM_VERSION_MAJOR >= 11
+        auto callval = orig->getCalledOperand();
+#else
+        auto callval = orig->getCalledValue();
+#endif
+        Value *dif0 = Builder2.CreateFDiv(
+            Builder2.CreateFMul(diffe(orig, Builder2), x),
+            Builder2.CreateFMul(
+                ConstantFP::get(x->getType(), 3),
+                Builder2.CreateCall(orig->getFunctionType(), callval, args)));
+        addToDiffe(orig->getArgOperand(0), dif0, Builder2, x->getType());
+        return;
+      }
+
       if (funcName == "tanhf" || funcName == "tanh") {
         if (gutils->knownRecomputeHeuristic.find(orig) !=
             gutils->knownRecomputeHeuristic.end()) {
@@ -4201,9 +4233,9 @@ class AdjointGenerator
                                       getIndex(orig, CacheType::Self));
             }
           }
+          eraseIfUnused(*orig);
           if (Mode == DerivativeMode::ReverseModePrimal ||
               gutils->isConstantInstruction(orig)) {
-            eraseIfUnused(*orig);
             return;
           }
 
@@ -4244,9 +4276,9 @@ class AdjointGenerator
                                       getIndex(orig, CacheType::Self));
             }
           }
+          eraseIfUnused(*orig);
           if (Mode == DerivativeMode::ReverseModePrimal ||
               gutils->isConstantInstruction(orig)) {
-            eraseIfUnused(*orig);
             return;
           }
 
@@ -4288,9 +4320,9 @@ class AdjointGenerator
                                       getIndex(orig, CacheType::Self));
             }
           }
+          eraseIfUnused(*orig);
           if (Mode == DerivativeMode::ReverseModePrimal ||
               gutils->isConstantInstruction(orig)) {
-            eraseIfUnused(*orig);
             return;
           }
 

enzyme/test/Enzyme/ReverseMode/cabs.ll

@@ -20,12 +20,11 @@ declare double @__enzyme_autodiff(double (double, double)*, ...)
 
 ; CHECK: define internal { double, double } @diffetester(double %x, double %y, double %differeturn) {
 ; CHECK-NEXT: entry:
-; CHECK-NEXT:   %call = call double @cabs(double %x, double %y)
 ; CHECK-NEXT:   %0 = call fast double @cabs(double %x, double %y)
 ; CHECK-NEXT:   %1 = fdiv fast double %differeturn, %0
 ; CHECK-NEXT:   %2 = fmul fast double %x, %1
 ; CHECK-NEXT:   %3 = fmul fast double %y, %1
 ; CHECK-NEXT:   %4 = insertvalue { double, double } undef, double %2, 0
 ; CHECK-NEXT:   %5 = insertvalue { double, double } %4, double %3, 1
 ; CHECK-NEXT:   ret { double, double } %5
-; CHECK-NEXT: }
+; CHECK-NEXT: }

enzyme/test/Enzyme/ReverseMode/cbrt.ll

@@ -0,0 +1,29 @@
+; RUN: %opt < %s %loadEnzyme -enzyme -enzyme-preopt=false -mem2reg -sroa -instsimplify -simplifycfg -adce -S | FileCheck %s
+
+; Function Attrs: nounwind readnone uwtable
+define double @tester(double %x) {
+entry:
+  %call = call double @cbrt(double %x)
+  ret double %call
+}
+
+define double @test_derivative(double %x) {
+entry:
+  %0 = tail call double (double (double)*, ...) @__enzyme_autodiff(double (double)* nonnull @tester, double %x)
+  ret double %0
+}
+
+declare double @cbrt(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 @cbrt(double %x)
+; CHECK-NEXT:   %1 = fmul fast double 3.000000e+00, %0
+; CHECK-NEXT:   %2 = fmul fast double %differeturn, %x
+; CHECK-NEXT:   %3 = fdiv fast double %2, %1
+; CHECK-NEXT:   %4 = insertvalue { double } undef, double %3, 0
+; CHECK-NEXT:   ret { double } %4
+; CHECK-NEXT: }