Bug#797626: llvm-toolchain-3.6: apply InstCombine patch for rustc

[Ximin Luo]

Source: llvm-toolchain-3.6
Severity: important
Tags: upstream patch

Dear Maintainer,

Please apply the attached patch. The origin is:

http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20150622/282940.html

and it is necessary to make later versions of rustc compile correctly, see 

https://github.com/rust-lang/rust/issues/26468

I have tested the patch against 1:3.6.2-1 and it applies cleanly with an offset.

Thanks,

X

-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'unstable'), (500, 'stable'), (1, 
'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.0.0-2-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

diff --git a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index e7a4533..c566eb0 100644
--- a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -749,10 +749,20 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
   // where there are several consecutive memory accesses to the same location,
   // separated by a few arithmetic operations.
   BasicBlock::iterator BBI = &LI;
-  if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6))
+  if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6)) {
+    if (LoadInst *NLI = dyn_cast<LoadInst>(AvailableVal)) {
+      unsigned KnownIDs[] = {
+        LLVMContext::MD_range,
+        LLVMContext::MD_invariant_load,
+        LLVMContext::MD_nonnull,
+      };
+      combineMetadata(NLI, &LI, KnownIDs);
+    };
+
     return ReplaceInstUsesWith(
         LI, Builder->CreateBitOrPointerCast(AvailableVal, LI.getType(),
                                             LI.getName() + ".cast"));
+  }
 
   // load(gep null, ...) -> unreachable
   if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
diff --git a/test/Transforms/InstCombine/load-range-metadata.ll b/test/Transforms/InstCombine/load-range-metadata.ll
new file mode 100644
index 0000000..8404499
--- /dev/null
+++ b/test/Transforms/InstCombine/load-range-metadata.ll
@@ -0,0 +1,19 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+target datalayout = "e-m:e-p:64:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+; CHECK-LABEL: @test_load_load_combine_range(
+; CHECK: %[[V:.*]] = load i32, i32* %{{.*}}, !range ![[MD:[0-9]+]]
+; CHECK: store i32 %[[V]], i32* %1
+; CHECK: store i32 %[[V]], i32* %2
+define void @test_load_load_combine_range(i32*, i32*, i32*) {
+  %a = load i32, i32* %0, !range !0
+  %b = load i32, i32* %0, !range !1
+  store i32 %a, i32* %1
+  store i32 %b, i32* %2
+  ret void
+}
+
+; CHECK: ![[MD]] = !{i32 0, i32 1, i32 8, i32 9}
+!0 = !{ i32 0, i32 1 }
+!1 = !{ i32 8, i32 9 }