[InstCombine] Fix incorrect usage of getPrimitiveSizeInBits when we should be using the element size for vectors

[craig.topper]

Summary

For vectors, getPrimitiveSizeInBits returns the full vector width. This code should using the element size for vectors. This could be fixed by calling getScalarSizeInBits, but its even easier to just get it from the APInt we're checking.

[spatel]

LGTM

lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

if (match(&I, m_Mul(m_Shl(m_Value(NewOp), m_Constant(C2)),
           Shl->isNotMinSignedValue())
         BO->setHasNoSignedWrap();
       return BO;
     }
 
     if (match(&I, m_Mul(m_Value(NewOp), m_Constant(C1)))) {
       // Replace X*(2^C) with X << C, where C is either a scalar or a vector.
       if (Constant *NewCst = getLogBase2(NewOp->getType(), C1)) {
-        unsigned Width = NewCst->getType()->getPrimitiveSizeInBits();
         BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
 
         if (I.hasNoUnsignedWrap())
           Shl->setHasNoUnsignedWrap();
         if (I.hasNoSignedWrap()) {
           const APInt *V;
-          if (match(NewCst, m_APInt(V)) && *V != Width - 1)
+          if (match(NewCst, m_APInt(V)) && *V != V->getBitWidth() - 1)
             Shl->setHasNoSignedWrap();
         }
 
         return Shl;
       }
     }
   }
 

test/Transforms/InstCombine/mul.ll

 ; CHECK-NEXT:    ret i32 [[MUL]]
 ;
   %mul = mul nsw i32 %X, -2147483648
   ret i32 %mul
 }
 
 define <2 x i32> @test32vec(<2 x i32> %X) {
 ; CHECK-LABEL: @test32vec(
-; CHECK-NEXT:    [[MUL:%.*]] = shl nsw <2 x i32> [[X:%.*]], <i32 31, i32 31>
+; CHECK-NEXT:    [[MUL:%.*]] = shl <2 x i32> [[X:%.*]], <i32 31, i32 31>
 ; CHECK-NEXT:    ret <2 x i32> [[MUL]]
 ;
   %mul = mul nsw <2 x i32> %X, <i32 -2147483648, i32 -2147483648>
   ret <2 x i32> %mul
 }
 
 define i32 @test33(i32 %X) {
 ; CHECK-LABEL: @test33(