backport "[InstCombine] Transform !range metadata to !nonnull when combining loads"

lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

@@ -380,8 +380,16 @@ static LoadInst *combineLoadToNewType(InstCombiner &IC, LoadInst &LI, Type *NewT
       break;
     case LLVMContext::MD_range:
       // FIXME: It would be nice to propagate this in some way, but the type
-      // conversions make it hard. If the new type is a pointer, we could
-      // translate it to !nonnull metadata.
+      // conversions make it hard.
+
+      // If it's a pointer now and the range does not contain 0, make it !nonnull.
+      if (NewTy->isPointerTy()) {
+        unsigned BitWidth = IC.getDataLayout().getTypeSizeInBits(NewTy);
+        if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) {
+          MDNode *NN = MDNode::get(LI.getContext(), None);
+          NewLoad->setMetadata(LLVMContext::MD_nonnull, NN);
+        }
+      }
       break;
     }
   }

test/Transforms/InstCombine/PR30597.ll

@@ -0,0 +1,32 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: readonly uwtable
+define i1 @dot_ref_s(i32** noalias nocapture readonly dereferenceable(8)) {
+entry-block:
+  %loadedptr = load i32*, i32** %0, align 8, !nonnull !0
+  %ptrtoint = ptrtoint i32* %loadedptr to i64
+  %inttoptr = inttoptr i64 %ptrtoint to i32*
+  %switchtmp = icmp eq i32* %inttoptr, null
+  ret i1 %switchtmp
+
+; CHECK-LABEL: @dot_ref_s
+; CHECK-NEXT: entry-block:
+; CHECK-NEXT: ret i1 false
+}
+
+; Function Attrs: readonly uwtable
+define i64* @function(i64* noalias nocapture readonly dereferenceable(8)) {
+entry-block:
+  %loaded = load i64, i64* %0, align 8, !range !1
+  %inttoptr = inttoptr i64 %loaded to i64*
+  ret i64* %inttoptr
+; CHECK-LABEL: @function
+; CHECK: %{{.+}} = load i64*, i64** %{{.+}}, align 8, !nonnull
+}
+
+
+!0 = !{}
+!1 = !{i64 1, i64 140737488355327}