[PATCH] D25376: [InstCombine] Don't unpack arrays that are too large

[Davide Italiano via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL283599: [InstCombine] Don't unpack arrays that are too large (authored by davide).

Changed prior to commit:
  https://reviews.llvm.org/D25376?vs=73965&id=73985#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D25376

Files:
  llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
  llvm/trunk/test/Transforms/InstCombine/unpack-fca.ll


Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -583,6 +583,13 @@
         UndefValue::get(T), NewLoad, 0, Name));
     }
 
+    // Bail out if the array is too large. Ideally we would like to optimize
+    // arrays of arbitrary size but this has a terrible impact on compile time.
+    // The threshold here is chosen arbitrarily, maybe needs a little bit of
+    // tuning.
+    if (NumElements > 1024)
+      return nullptr;
+
     const DataLayout &DL = IC.getDataLayout();
     auto EltSize = DL.getTypeAllocSize(ET);
     auto Align = LI.getAlignment();
Index: llvm/trunk/test/Transforms/InstCombine/unpack-fca.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/unpack-fca.ll
+++ llvm/trunk/test/Transforms/InstCombine/unpack-fca.ll
@@ -179,6 +179,14 @@
   ret [2 x %B] %1
 }
 
+define [2000 x %B] @loadLargeArrayOfB([2000 x %B]* %ab.ptr) {
+; CHECK-LABEL: loadLargeArrayOfB
+; CHECK-NEXT: load [2000 x %B], [2000 x %B]* %ab.ptr, align 8
+; CHECK-NEXT: ret [2000 x %B]
+  %1 = load [2000 x %B], [2000 x %B]* %ab.ptr, align 8
+  ret [2000 x %B] %1
+}
+
 %struct.S = type <{ i8, %struct.T }>
 %struct.T = type { i32, i32 }
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D25376.73985.patch
Type: text/x-patch
Size: 1438 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20161007/2f0c258f/attachment.bin>