3 files changed, 44 insertions, 6 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 5631bd0..661b047 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2576,12 +2576,21 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
     } else if (isa<VectorType>(Op1->getType())) {
       if (isa<ConstantAggregateZero>(Op1))
         return ReplaceInstUsesWith(I, Op1);
-      
-      // As above, vector X*splat(1.0) -> X in all defined cases.
-      if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1))
-        if (ConstantFP *F = dyn_cast_or_null<ConstantFP>(Op1V->getSplatValue()))
-          if (F->isExactlyValue(1.0))
-            return ReplaceInstUsesWith(I, Op0);
+
+      if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1)) {
+        if (Op1V->isAllOnesValue())              // X * -1 == 0 - X
+          return BinaryOperator::CreateNeg(Op0, I.getName());
+
+        // As above, vector X*splat(1.0) -> X in all defined cases.
+        if (Constant *Splat = Op1V->getSplatValue()) {
+          if (ConstantFP *F = dyn_cast<ConstantFP>(Splat))
+            if (F->isExactlyValue(1.0))
+              return ReplaceInstUsesWith(I, Op0);
+          if (ConstantInt *CI = dyn_cast<ConstantInt>(Splat))
+            if (CI->equalsInt(1))
+              return ReplaceInstUsesWith(I, Op0);
+        }
+      }
     }
     
     if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
@@ -2856,6 +2865,13 @@ Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
   if (I.getType() == Type::Int1Ty)
     return ReplaceInstUsesWith(I, Op0);
 
+  if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1)) {
+    if (ConstantInt *X = cast_or_null<ConstantInt>(Op1V->getSplatValue()))
+      // div X, 1 == X
+      if (X->isOne())
+        return ReplaceInstUsesWith(I, Op0);
+  }
+
   return 0;
 }
 
diff --git a/test/Transforms/InstCombine/2008-11-27-IDivVector.ll b/test/Transforms/InstCombine/2008-11-27-IDivVector.ll
new file mode 100644
index 0000000..4275e11
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-11-27-IDivVector.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep div
+
+define <2 x i8> @f(<2 x i8> %x) {
+  %A = udiv <2 x i8> %x, <i8 1, i8 1>
+  ret <2 x i8> %A
+}
+
+define <2 x i8> @g(<2 x i8> %x) {
+  %A = sdiv <2 x i8> %x, <i8 1, i8 1>
+  ret <2 x i8> %A
+}
diff --git a/test/Transforms/InstCombine/2008-11-27-MultiplyIntVec.ll b/test/Transforms/InstCombine/2008-11-27-MultiplyIntVec.ll
new file mode 100644
index 0000000..544e9ab
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-11-27-MultiplyIntVec.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep mul
+
+define <2 x i8> @f(<2 x i8> %x) {
+  %A = mul <2 x i8> %x, <i8 1, i8 1>
+  ret <2 x i8> %A
+}
+
+define <2 x i8> @g(<2 x i8> %x) {
+  %A = mul <2 x i8> %x, <i8 -1, i8 -1>
+  ret <2 x i8> %A
+}