[PATCH] [InstSimplify] Support constant folding to vector of pointers

[Matt Arsenault]

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Comment at: lib/Analysis/ConstantFolding.cpp:59
@@ -59,1 +58,3 @@
+  if (C->isAllOnesValue() && !DestTy->isX86_MMXTy() &&
+      !DestTy->isPtrOrPtrVectorTy()) // don't get ones for ptr types!
     return Constant::getAllOnesValue(DestTy);
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Comment should be capitalized.


Why do you need this check on the isAllOnesValue() and not the isNullValue() case?

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Comment at: lib/Analysis/ConstantFolding.cpp:200
@@ +199,3 @@
+  // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>) and
+  //         bitcast (<1 x i128> <i128 -1> to <2 x i8*>)
+  bool IsDstEltTyPtr = DstEltTy->isPointerTy();
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Slightly misleading comment? This bitcast isn't allowed and this needs to be an inttoptr

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Comment at: lib/Analysis/ConstantFolding.cpp:203-204
@@ -199,3 +202,4 @@
   unsigned Ratio = NumDstElt/NumSrcElt;
-  unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
+  unsigned DstBitSize = IsDstEltTyPtr ? TD.getPointerTypeSizeInBits(DstEltTy)
+                                      : DstEltTy->getPrimitiveSizeInBits();
 
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You don't need to do this check to get the type size yourself. TD.getTypeSizeInBits checks the pointeriness for you

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Comment at: test/Transforms/InstSimplify/vector_ptr_bitcast.ll:6-8
@@ +5,5 @@
+
+ at a = private unnamed_addr constant %mst { i8* inttoptr (i64 -1 to i8*),
+                                          i8* inttoptr (i64 -1 to i8*)},
+                                          align 8
+
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Another testcase that uses different sized pointers that require a trunc might be useful. Also one that uses constants other than -1

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Comment at: test/Transforms/InstSimplify/vector_ptr_bitcast.ll:12-13
@@ +11,4 @@
+  %x = load <2 x i8*>* bitcast (%mst* @a to <2 x i8*>*), align 8
+  %b = extractelement <2 x i8*> %x, i32 0
+  ; CHECK-LABEL: @fn
+  ; CHECK-NEXT: ret void
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Test should probably do something with this so there is something to check other than deleting all of the code

http://reviews.llvm.org/D5834