[PATCH] Correctly handle range metadata when hoisting instructions out of then/else into if blocks

[Björn Steinbrink]

When there are loads in the then and else blocks, we can still hoist
them up into the if block, but we have to take caret to adjust the range
metadata.

http://reviews.llvm.org/D4595

Files:
  lib/Transforms/Utils/SimplifyCFG.cpp
  test/Transforms/SimplifyCFG/hoist-with-range.ll

Index: lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyCFG.cpp
+++ lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1040,6 +1040,10 @@
     if (!I2->use_empty())
       I2->replaceAllUsesWith(I1);
     I1->intersectOptionalDataWith(I2);
+    I1->setMetadata(LLVMContext::MD_range,
+        MDNode::getMostGenericRange(
+          I1->getMetadata(LLVMContext::MD_range),
+          I2->getMetadata(LLVMContext::MD_range)));
     I2->eraseFromParent();
     Changed = true;
 
Index: test/Transforms/SimplifyCFG/hoist-with-range.ll
===================================================================
--- /dev/null
+++ test/Transforms/SimplifyCFG/hoist-with-range.ll
@@ -0,0 +1,20 @@
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+define void @foo(i1 %c, i8* %p) {
+; CHECK: if:
+; CHECK-NEXT: load i8* %p, !range !0
+; CHECK: !0 = metadata !{i8 0, i8 1, i8 3, i8 5}
+if:
+  br i1 %c, label %then, label %else
+then:
+  %t = load i8* %p, !range !0
+  br label %out
+else:
+  %e = load i8* %p, !range !1
+  br label %out
+out:
+  ret void
+}
+
+!0 = metadata !{ i8 0, i8 1 }
+!1 = metadata !{ i8 3, i8 5 }
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