InstSimplify: stripAndComputeConstantOffsets can be called with vectors of pointers too.

Prepare it for vectors of pointers and handle simple cases. We don't handle
complicated cases because accumulateConstantOffset bails on pointer vectors.
Fixes selfhost on i386.

llvm-svn: 174179

2 files changed, 29 insertions, 10 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index e296215442c..34ff64d9004 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -667,9 +667,9 @@ Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
 /// This is very similar to GetPointerBaseWithConstantOffset except it doesn't
 /// follow non-inbounds geps. This allows it to remain usable for icmp ult/etc.
 /// folding.
-static ConstantInt *stripAndComputeConstantOffsets(const DataLayout *TD,
-                                                   Value *&V) {
-  assert(V->getType()->isPointerTy());
+static Constant *stripAndComputeConstantOffsets(const DataLayout *TD,
+                                                Value *&V) {
+  assert(V->getType()->getScalarType()->isPointerTy());
 
   // Without DataLayout, just be conservative for now. Theoretically, more could
   // be done in this case.
@@ -697,11 +697,16 @@ static ConstantInt *stripAndComputeConstantOffsets(const DataLayout *TD,
     } else {
       break;
     }
-    assert(V->getType()->isPointerTy() && "Unexpected operand type!");
+    assert(V->getType()->getScalarType()->isPointerTy() &&
+           "Unexpected operand type!");
   } while (Visited.insert(V));
 
   Type *IntPtrTy = TD->getIntPtrType(V->getContext());
-  return cast<ConstantInt>(ConstantInt::get(IntPtrTy, Offset));
+  Constant *OffsetIntPtr = ConstantInt::get(IntPtrTy, Offset);
+  if (V->getType()->isVectorTy())
+    return ConstantVector::getSplat(V->getType()->getVectorNumElements(),
+                                    OffsetIntPtr);
+  return OffsetIntPtr;
 }
 
 /// \brief Compute the constant difference between two pointer values.
@@ -1758,8 +1763,8 @@ static Constant *computePointerICmp(const DataLayout *TD,
   // numerous hazards. AliasAnalysis and its utilities rely on special rules
   // governing loads and stores which don't apply to icmps. Also, AliasAnalysis
   // doesn't need to guarantee pointer inequality when it says NoAlias.
-  ConstantInt *LHSOffset = stripAndComputeConstantOffsets(TD, LHS);
-  ConstantInt *RHSOffset = stripAndComputeConstantOffsets(TD, RHS);
+  Constant *LHSOffset = stripAndComputeConstantOffsets(TD, LHS);
+  Constant *RHSOffset = stripAndComputeConstantOffsets(TD, RHS);
 
   // If LHS and RHS are related via constant offsets to the same base
   // value, we can replace it with an icmp which just compares the offsets.
@@ -1799,11 +1804,14 @@ static Constant *computePointerICmp(const DataLayout *TD,
     // address, due to canonicalization and constant folding.
     if (isa<AllocaInst>(LHS) &&
         (isa<AllocaInst>(RHS) || isa<GlobalVariable>(RHS))) {
+      ConstantInt *LHSOffsetCI = dyn_cast<ConstantInt>(LHSOffset);
+      ConstantInt *RHSOffsetCI = dyn_cast<ConstantInt>(RHSOffset);
       uint64_t LHSSize, RHSSize;
-      if (getObjectSize(LHS, LHSSize, TD, TLI) &&
+      if (LHSOffsetCI && RHSOffsetCI &&
+          getObjectSize(LHS, LHSSize, TD, TLI) &&
           getObjectSize(RHS, RHSSize, TD, TLI)) {
-        const APInt &LHSOffsetValue = LHSOffset->getValue();
-        const APInt &RHSOffsetValue = RHSOffset->getValue();
+        const APInt &LHSOffsetValue = LHSOffsetCI->getValue();
+        const APInt &RHSOffsetValue = RHSOffsetCI->getValue();
         if (!LHSOffsetValue.isNegative() &&
             !RHSOffsetValue.isNegative() &&
             LHSOffsetValue.ult(LHSSize) &&
diff --git a/llvm/test/Transforms/InstSimplify/ptr_diff.ll b/llvm/test/Transforms/InstSimplify/ptr_diff.ll
index 1eb1fd4c097..86516280696 100644
--- a/llvm/test/Transforms/InstSimplify/ptr_diff.ll
+++ b/llvm/test/Transforms/InstSimplify/ptr_diff.ll
@@ -46,3 +46,14 @@ define i64 @ptrdiff3(i8* %ptr) {
   %diff = sub i64 %last.int, %first.int
   ret i64 %diff
 }
+
+define <4 x i32> @ptrdiff4(<4 x i8*> %arg) nounwind {
+; Handle simple cases of vectors of pointers.
+; CHECK: @ptrdiff4
+; CHECK: ret <4 x i32> zeroinitializer
+  %p1 = ptrtoint <4 x i8*> %arg to <4 x i32>
+  %bc = bitcast <4 x i8*> %arg to <4 x i32*>
+  %p2 = ptrtoint <4 x i32*> %bc to <4 x i32>
+  %sub = sub <4 x i32> %p1, %p2
+  ret <4 x i32> %sub
+}