[PATCH] [SelectionDAG] Fix PR23603.

[Sanjoy Das]

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D10075

Files:
  llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  llvm/trunk/test/CodeGen/X86/pr23603.ll

Index: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2848,7 +2848,17 @@
 
   bool isVolatile = I.isVolatile();
   bool isNonTemporal = I.getMetadata(LLVMContext::MD_nontemporal) != nullptr;
-  bool isInvariant = I.getMetadata(LLVMContext::MD_invariant_load) != nullptr;
+
+  // The IR notion of invariant_load only guarantees that all *non-faulting*
+  // invariant loads result in the same value.  The MI notion of invariant load
+  // guarantees that the load can be legally moved to any location within its
+  // containing function.  The MI notion of invariant_load is stronger than the
+  // IR notion of invariant_load -- an MI invariant_load is an IR invariant_load
+  // with a guarantee that the location being loaded from is dereferenceable
+  // throughout the function's lifetime.
+
+  bool isInvariant = I.getMetadata(LLVMContext::MD_invariant_load) != nullptr &&
+    isDereferenceablePointer(SV, *DAG.getTarget().getDataLayout());
   unsigned Alignment = I.getAlignment();
 
   AAMDNodes AAInfo;
Index: llvm/trunk/test/CodeGen/X86/pr23603.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/pr23603.ll
+++ llvm/trunk/test/CodeGen/X86/pr23603.ll
@@ -0,0 +1,24 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+
+declare void @free_v()
+
+define void @f(i32* %x, i32 %c32, i32* %y) {
+; CHECK-LABEL: f
+ entry:
+  %v = load i32, i32* %x, !invariant.load !0
+; CHECK: movl (%rdi), %ebx
+; CHECK: free_v
+; CHECK-NOT: movl (%rdi), %ebx
+  call void @free_v()
+  %c = icmp ne i32 %c32, 0
+  br i1 %c, label %left, label %merge
+
+ left:
+  store i32 %v, i32* %y
+  br label %merge
+
+ merge:
+  ret void
+}
+
+!0 = !{}

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