[PATCH] [IC] Turn non-null MD on pointer loads to range MD on integer loads.

[Charles Davis]

Hi chandlerc,

This change fixes the FIXME that you recently added when you committed
(a modified version of) my patch.  When `InstCombine` combines a load and
store of an pointer to those of an equivalently-sized integer, it currently
drops any `!nonnull` metadata that might be present.  This change replaces
`!nonnull` metadata with `!range !{ 1, -1 }` metadata instead.

(Yes, everything with my Gmail account is OK, now. Thanks for your help!)

http://reviews.llvm.org/D7621

Files:
  lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
  test/Transforms/InstCombine/loadstore-metadata.ll

Index: lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -335,10 +335,20 @@
       break;
 
     case LLVMContext::MD_nonnull:
-      // FIXME: We should translate this into range metadata for integer types
-      // and vice versa.
       if (NewTy->isPointerTy())
         NewLoad->setMetadata(ID, N);
+      else {
+        // If it's integral, translate it to !range metadata.
+        auto *ITy = dyn_cast<IntegerType>(NewTy);
+        if (!ITy) break;
+        Metadata *Range[] = {
+          ConstantAsMetadata::get(IC.Builder->getIntN(ITy->getBitWidth(), 1)),
+          ConstantAsMetadata::get(IC.Builder->getIntN(ITy->getBitWidth(),
+                                                      ITy->getBitMask()))
+        };
+        NewLoad->setMetadata(LLVMContext::MD_range,
+                             MDTuple::get(NewLoad->getContext(), Range));
+      }
       break;
 
     case LLVMContext::MD_range:
Index: test/Transforms/InstCombine/loadstore-metadata.ll
===================================================================
--- test/Transforms/InstCombine/loadstore-metadata.ll
+++ test/Transforms/InstCombine/loadstore-metadata.ll
@@ -83,10 +83,9 @@
 define void @test_load_cast_combine_nonnull(float** %ptr) {
 ; We can't preserve nonnull metadata when converting a load of a pointer to
 ; a load of an integer.
-; FIXME: We should really transform this into range metadata and vice versa.
 ;
 ; CHECK-LABEL: @test_load_cast_combine_nonnull(
-; CHECK: %[[V:.*]] = load i64* %{{.*}}
+; CHECK: %[[V:.*]] = load i64* %{{.*}}, !range
 ; CHECK-NOT: !nonnull
 ; CHECK: store i64 %[[V]], i64*
 entry:

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