Handle maxpd (rust-lang#690)

Author: wsmoses

enzyme/Enzyme/AdjointGenerator.h

@@ -10494,6 +10494,43 @@ class AdjointGenerator
         }
       }
     }
+#if LLVM_VERSION_MAJOR >= 11
+    if (auto assembly = dyn_cast<InlineAsm>(orig->getCalledOperand()))
+#else
+    if (auto assembly = dyn_cast<InlineAsm>(orig->getCalledValue()))
+#endif
+    {
+      if (assembly->getAsmString() == "maxpd $1, $0") {
+        if (Mode == DerivativeMode::ReverseModePrimal ||
+            gutils->isConstantInstruction(orig)) {
+
+          if (gutils->knownRecomputeHeuristic.find(orig) !=
+              gutils->knownRecomputeHeuristic.end()) {
+            if (!gutils->knownRecomputeHeuristic[orig]) {
+              gutils->cacheForReverse(BuilderZ, newCall,
+                                      getIndex(orig, CacheType::Self));
+            }
+          }
+          eraseIfUnused(*orig);
+          return;
+        }
+
+        SmallVector<Value *, 2> orig_ops(orig->getNumOperands());
+        for (unsigned i = 0; i < orig->getNumOperands(); ++i) {
+          orig_ops[i] = orig->getOperand(i);
+        }
+        handleAdjointForIntrinsic(Intrinsic::maxnum, *orig, orig_ops);
+        if (gutils->knownRecomputeHeuristic.find(orig) !=
+            gutils->knownRecomputeHeuristic.end()) {
+          if (!gutils->knownRecomputeHeuristic[orig]) {
+            gutils->cacheForReverse(BuilderZ, newCall,
+                                    getIndex(orig, CacheType::Self));
+          }
+        }
+        eraseIfUnused(*orig);
+        return;
+      }
+    }
 
     if (called && isAllocationFunction(*called, gutils->TLI)) {
 

enzyme/test/Enzyme/ReverseMode/maxpd.ll

@@ -0,0 +1,23 @@
+; RUN: %opt < %s %loadEnzyme -enzyme -enzyme-preopt=false -mem2reg -early-cse -simplifycfg -S | FileCheck %s
+
+define <2 x double> @pmax(<2 x double> %a, <2 x double> %b) {
+  %r = call <2 x double> asm "maxpd $1, $0", "=x,x,0,~{dirflag},~{fpsr},~{flags}"(<2 x double> %a, <2 x double> %b)
+  ret <2 x double> %r
+}
+
+declare { <2 x double>, <2 x double> } @__enzyme_autodiff(...)
+
+define { <2 x double>, <2 x double> } @test_derivative(<2 x double> %x, <2 x double> %y) {
+entry:
+  %0 = tail call { <2 x double>, <2 x double> } (...) @__enzyme_autodiff(<2 x double> (<2 x double>, <2 x double>)* @pmax, <2 x double> %x, <2 x double> %y)
+  ret { <2 x double>, <2 x double> } %0
+}
+
+; CHECK: define internal { <2 x double>, <2 x double> } @diffepmax(<2 x double> %a, <2 x double> %b, <2 x double> %differeturn) 
+; CHECK:   %r = call <2 x double> asm "maxpd $1, $0", "=x,x,0,~{dirflag},~{fpsr},~{flags}"(<2 x double> %a, <2 x double> %b) 
+; CHECK-NEXT:   %[[i0:.+]] = fcmp fast olt <2 x double> %a, %b
+; CHECK-NEXT:   %[[i1:.+]] = select {{(fast )?}}<2 x i1> %[[i0]], <2 x double> zeroinitializer, <2 x double> %differeturn
+; CHECK-NEXT:   %[[i2:.+]] = select {{(fast )?}}<2 x i1> %[[i0]], <2 x double> %differeturn, <2 x double> zeroinitializer
+; CHECK-NEXT:   %[[i3:.+]] = insertvalue { <2 x double>, <2 x double> } undef, <2 x double> %[[i1]], 0
+; CHECK-NEXT:   %[[i4:.+]] = insertvalue { <2 x double>, <2 x double> } %[[i3]], <2 x double> %[[i2]], 1
+; CHECK-NEXT:   ret { <2 x double>, <2 x double> } %[[i4]]