[PATCH] Fix lint assert on integer vector division

[Matt Arsenault]

  Fix checking undef vector elements

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

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D1408?vs=3490&id=3491#toc

Files:
  lib/Analysis/Lint.cpp
  test/Analysis/Lint/check-zero-divide.ll
  test/Analysis/Lint/lit.local.cfg

Index: lib/Analysis/Lint.cpp
===================================================================
--- lib/Analysis/Lint.cpp
+++ lib/Analysis/Lint.cpp
@@ -504,14 +504,42 @@
             "Undefined result: Shift count out of range", &I);
 }
 
-static bool isZero(Value *V, DataLayout *TD) {
+static bool isZero(Value *V, DataLayout *DL) {
   // Assume undef could be zero.
-  if (isa<UndefValue>(V)) return true;
+  if (isa<UndefValue>(V))
+    return true;
 
-  unsigned BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
-  APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
-  ComputeMaskedBits(V, KnownZero, KnownOne, TD);
-  return KnownZero.isAllOnesValue();
+  VectorType *VecTy = dyn_cast<VectorType>(V->getType());
+  if (!VecTy) {
+    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)
+    return false;
+
+  if (C->isZeroValue())
+    return true;
+
+  // For a vector, KnownZero will only be true if all values are zero, so check
+  // this per component
+  unsigned BitWidth = VecTy->getElementType()->getIntegerBitWidth();
+  for (unsigned I = 0, N = VecTy->getNumElements(); I != N; ++I) {
+    Constant *Elem = C->getAggregateElement(I);
+    if (isa<UndefValue>(Elem))
+      return true;
+
+    APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
+    ComputeMaskedBits(Elem, KnownZero, KnownOne, DL);
+    if (KnownZero.isAllOnesValue())
+      return true;
+  }
+
+  return false;
 }
 
 void Lint::visitSDiv(BinaryOperator &I) {
Index: test/Analysis/Lint/check-zero-divide.ll
===================================================================
--- /dev/null
+++ test/Analysis/Lint/check-zero-divide.ll
@@ -0,0 +1,78 @@
+; 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>
+  ret <2 x i32> %b
+}
+
+define <2 x i32> @use_vector_srem(<2 x i32> %a) nounwind {
+  %b = srem <2 x i32> %a, <i32 5, i32 8>
+  ret <2 x i32> %b
+}
+
+define <2 x i32> @use_vector_udiv(<2 x i32> %a) nounwind {
+  %b = udiv <2 x i32> %a, <i32 5, i32 8>
+  ret <2 x i32> %b
+}
+
+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
+}
+
+define i32 @use_sdiv_by_zero(i32 %a) nounwind {
+; CHECK: Undefined behavior: Division by zero
+; CHECK-NEXT: %b = sdiv i32 %a, 0
+  %b = sdiv i32 %a, 0
+  ret i32 %b
+}
+
+define i32 @use_sdiv_by_zeroinitializer(i32 %a) nounwind {
+; CHECK: Undefined behavior: Division by zero
+; CHECK-NEXT: %b = sdiv i32 %a, 0
+  %b = sdiv i32 %a, zeroinitializer
+   ret i32 %b
+}
+
+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
+}
+
+define <2 x i32> @use_vector_sdiv_by_undef_x(<2 x i32> %a) nounwind {
+; CHECK: Undefined behavior: Division by zero
+; CHECK-NEXT: %b = sdiv <2 x i32> %a, <i32 undef, i32 5>
+  %b = sdiv <2 x i32> %a, <i32 undef, i32 5>
+  ret <2 x i32> %b
+}
+
+define <2 x i32> @use_vector_sdiv_by_undef_y(<2 x i32> %a) nounwind {
+; CHECK: Undefined behavior: Division by zero
+; CHECK-NEXT: %b = sdiv <2 x i32> %a, <i32 5, i32 undef>
+  %b = sdiv <2 x i32> %a, <i32 5, i32 undef>
+  ret <2 x i32> %b
+}
+
+define <2 x i32> @use_vector_sdiv_by_undef_xy(<2 x i32> %a) nounwind {
+; CHECK: Undefined behavior: Division by zero
+; CHECK-NEXT: %b = sdiv <2 x i32> %a, undef
+  %b = sdiv <2 x i32> %a, <i32 undef, i32 undef>
+  ret <2 x i32> %b
+}
+
Index: test/Analysis/Lint/lit.local.cfg
===================================================================
--- /dev/null
+++ test/Analysis/Lint/lit.local.cfg
@@ -0,0 +1 @@
+config.suffixes = ['.ll']
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