[PATCH] Fix lint assert on integer vector division

[Matt Arsenault]

  Make the zero check actually work for vectors

http://llvm-reviews.chandlerc.com/D1408

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D1408?vs=3487&id=3490#toc

Files:
  lib/Analysis/Lint.cpp
  test/Analysis/Lint/check-zero-vector.ll

Index: lib/Analysis/Lint.cpp
===================================================================
--- lib/Analysis/Lint.cpp
+++ lib/Analysis/Lint.cpp
@@ -509,10 +509,37 @@
   if (isa<UndefValue>(V))
     return true;
 
-  unsigned BitWidth = V->getType()->getScalarType()->getIntegerBitWidth();
-  APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
-  ComputeMaskedBits(V, KnownZero, KnownOne, DL);
-  return KnownZero.isAllOnesValue();
+  if (!V->getType()->isVectorTy()) {
+    unsigned BitWidth = V->getType()->getIntegerBitWidth();
+    APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
+    ComputeMaskedBits(V, KnownZero, KnownOne, DL);
+    return KnownZero.isAllOnesValue();
+  }
+
+  // Per-component check doesn't work with zeroinitializer
+  Constant *C = dyn_cast<Constant>(V);
+  if (C && C->isZeroValue())
+    return true;
+
+  // For a vector, this will only be true if all values are zero, so check this
+  // per component
+  ConstantDataSequential *CDS = dyn_cast<ConstantDataSequential>(C);
+  if (!CDS)
+    return false;
+
+  unsigned BitWidth = CDS->getElementType()->getIntegerBitWidth();
+  for (unsigned I = 0, N = CDS->getNumElements(); I != N; ++I) {
+    APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
+    Constant *Elem = CDS->getElementAsConstant(I);
+    if (isa<UndefValue>(Elem))
+      return true;
+
+    ComputeMaskedBits(Elem, KnownZero, KnownOne, DL);
+    if (KnownZero.isAllOnesValue())
+      return true;
+  }
+
+  return false;
 }
 
 void Lint::visitSDiv(BinaryOperator &I) {
Index: test/Analysis/Lint/check-zero-vector.ll
===================================================================
--- test/Analysis/Lint/check-zero-vector.ll
+++ test/Analysis/Lint/check-zero-vector.ll
@@ -1,4 +1,4 @@
-; RUN: opt -lint < %s
+; RUN: opt -lint -disable-output %s 2>&1 | FileCheck %s
 
 define <2 x i32> @use_vector_sdiv(<2 x i32> %a) nounwind {
   %b = sdiv <2 x i32> %a, <i32 5, i32 8>
@@ -18,4 +18,25 @@
 define <2 x i32> @use_vector_urem(<2 x i32> %a) nounwind {
   %b = urem <2 x i32> %a, <i32 5, i32 8>
   ret <2 x i32> %b
-}
\ No newline at end of file
+}
+
+define <2 x i32> @use_vector_sdiv_by_zero_x(<2 x i32> %a) nounwind {
+; CHECK: Undefined behavior: Division by zero
+; CHECK-NEXT: %b = sdiv <2 x i32> %a, <i32 0, i32 5>
+  %b = sdiv <2 x i32> %a, <i32 0, i32 5>
+  ret <2 x i32> %b
+}
+
+define <2 x i32> @use_vector_sdiv_by_zero_y(<2 x i32> %a) nounwind {
+; CHECK: Undefined behavior: Division by zero
+; CHECK-NEXT:  %b = sdiv <2 x i32> %a, <i32 4, i32 0>
+  %b = sdiv <2 x i32> %a, <i32 4, i32 0>
+  ret <2 x i32> %b
+}
+
+define <2 x i32> @use_vector_sdiv_by_zero_xy(<2 x i32> %a) nounwind {
+; CHECK: Undefined behavior: Division by zero
+; CHECK-NEXT: %b = sdiv <2 x i32> %a, zeroinitializer
+  %b = sdiv <2 x i32> %a, <i32 0, i32 0>
+  ret <2 x i32> %b
+}
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