From 8d75756c0792ffabf07b239440bc5c1fa48fb799 Mon Sep 17 00:00:00 2001
From: William Moses <gh@wsmoses.com>
Date: Tue, 27 Feb 2024 16:53:36 -0500
Subject: [PATCH] Correct complex inv (#1767)

---
 enzyme/Enzyme/InstructionDerivatives.td | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/enzyme/Enzyme/InstructionDerivatives.td b/enzyme/Enzyme/InstructionDerivatives.td
index 32b30bd8f9b4..6491fa032798 100644
--- a/enzyme/Enzyme/InstructionDerivatives.td
+++ b/enzyme/Enzyme/InstructionDerivatives.td
@@ -162,12 +162,20 @@ def CFNeg : SubRoutine<(Op (Op $re, $im):$z),
       (FNeg $re),
       (FNeg $im)
     )>;
+
+def Conj : SubRoutine<(Op (Op $re, $im):$z),
+    (ArrayRet
+      $re,
+      (FNeg $im)
+    )>;
+
 def CFExp : SubRoutine<(Op (Op $re, $im):$z),
     (ArrayRet
       (FMul (FExp $re):$exp, (FCos $im)),
       (FMul $exp, (FSin $im))
     )>;
 
+
 // Same function as the one being called
 def SameFunc {
 }
@@ -826,9 +834,10 @@ def : CallPattern<(Op (Op $x, $y):$z),
 def : CallPattern<(Op (Op $x, $y):$z),
                   ["cmplx_inv"],
                   [
-                    (CFDiv (CFNeg (DiffeRet)), (CFMul $z, $z)),
+					// Reverse mode needs to return the conjugate
+                    (Conj (CFDiv (CFNeg (Conj (DiffeRet))), (CFMul $z, $z))),
                   ],
-                  (ForwardFromSummedReverse),
+                  (CFDiv (CFNeg (Shadow $z)), (CFMul $z, $z)),
                   [ReadNone, NoUnwind]
                   >;