Backport "[SimplifyCFG] Hoisting invalidates metadata"

lib/Transforms/Utils/SimplifyCFG.cpp

@@ -2024,14 +2024,20 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetTransformInfo &TTI,
 
   // Move all 'aggressive' instructions, which are defined in the
   // conditional parts of the if's up to the dominating block.
-  if (IfBlock1)
+  if (IfBlock1) {
+    for (auto &I : *IfBlock1)
+      I.dropUnknownNonDebugMetadata();
     DomBlock->getInstList().splice(InsertPt->getIterator(),
                                    IfBlock1->getInstList(), IfBlock1->begin(),
                                    IfBlock1->getTerminator()->getIterator());
-  if (IfBlock2)
+  }
+  if (IfBlock2) {
+    for (auto &I : *IfBlock2)
+      I.dropUnknownNonDebugMetadata();
     DomBlock->getInstList().splice(InsertPt->getIterator(),
                                    IfBlock2->getInstList(), IfBlock2->begin(),
                                    IfBlock2->getTerminator()->getIterator());
+  }
 
   while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
     // Change the PHI node into a select instruction.

test/Transforms/SimplifyCFG/PR29163.ll

@@ -0,0 +1,31 @@
+; RUN: opt -S -simplifycfg < %s | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@GV = external constant i64*
+
+define i64* @test1(i1 %cond, i8* %P) {
+entry:
+  br i1 %cond, label %if, label %then
+
+then:
+  %bc = bitcast i8* %P to i64*
+  br label %join
+
+if:
+  %load = load i64*, i64** @GV, align 8, !dereferenceable !0
+  br label %join
+
+join:
+  %phi = phi i64* [ %bc, %then ], [ %load, %if ]
+  ret i64* %phi
+}
+
+; CHECK-LABEL: define i64* @test1(
+; CHECK: %[[bc:.*]] = bitcast i8* %P to i64*
+; CHECK: %[[load:.*]] = load i64*, i64** @GV, align 8{{$}}
+; CHECK: %[[phi:.*]] = select i1 %cond, i64* %[[load]], i64* %[[bc]]
+; CHECK: ret i64* %[[phi]]
+
+
+!0 = !{i64 8}