Fix trunc i1 (rust-lang#822)

Author: wsmoses

enzyme/Enzyme/TypeAnalysis/TypeAnalysis.cpp

@@ -1687,16 +1687,19 @@ void TypeAnalyzer::visitTruncInst(TruncInst &I) {
   size_t inSize = (DL.getTypeSizeInBits(I.getOperand(0)->getType()) + 7) / 8;
   size_t outSize = (DL.getTypeSizeInBits(I.getType()) + 7) / 8;
   if (direction & DOWN)
-    updateAnalysis(&I,
-                   getAnalysis(I.getOperand(0))
-                       .ShiftIndices(DL, /*off*/ 0, inSize, /*addOffset*/ 0)
-                       .ShiftIndices(DL, /*off*/ 0, outSize, /*addOffset*/ 0),
-                   &I);
+    if (outSize != 1)
+      updateAnalysis(&I,
+                     getAnalysis(I.getOperand(0))
+                         .ShiftIndices(DL, /*off*/ 0, inSize, /*addOffset*/ 0)
+                         .ShiftIndices(DL, /*off*/ 0, outSize, /*addOffset*/ 0),
+                     &I);
+  // Don't propagate up a trunc float -> i8
   if (direction & UP)
-    updateAnalysis(
-        I.getOperand(0),
-        getAnalysis(&I).ShiftIndices(DL, /*off*/ 0, outSize, /*addOffset*/ 0),
-        &I);
+    if (outSize != 1 || inSize == 1)
+      updateAnalysis(
+          I.getOperand(0),
+          getAnalysis(&I).ShiftIndices(DL, /*off*/ 0, outSize, /*addOffset*/ 0),
+          &I);
 }
 
 void TypeAnalyzer::visitZExtInst(ZExtInst &I) {

enzyme/test/TypeAnalysis/truncfloat.ll

@@ -0,0 +1,15 @@
+; RUN: %opt < %s %loadEnzyme -print-type-analysis -type-analysis-func=d -o /dev/null | FileCheck %s
+
+define i8 @d(double %x) {
+entry:
+  %bc = bitcast double %x to i64
+  %t = trunc i64 %bc to i8
+  ret i8 %t
+}
+
+; CHECK: d - {[-1]:Integer} |{[-1]:Float@double}:{}
+; CHECK-NEXT: double %x: {[-1]:Float@double}
+; CHECK-NEXT: entry
+; CHECK-NEXT:   %bc = bitcast double %x to i64: {[-1]:Float@double}
+; CHECK-NEXT:   %t = trunc i64 %bc to i8: {[-1]:Integer}
+; CHECK-NEXT:   ret i8 %t: {}